Whether Twitter someday takes its place in the stable of modern ways we interact with one another or eventually fades away like some old ruins, as far as I can tell it is a nearly completely novel model for communicating. "How exactly?" is a fine question. As I've begun collecting string on Twitter and spending an unhealthy amount of time Twittering and reading tweets myself, I've hit upon a few initial questions that are a starting point for thinking about how, at least, some small segment of the population is chatting today. Here are my top five four:

1) On Twitter, Who is the Audience? And Is It Different from the People You're Talking To?
This is the big one in my mind right now. A defining part of the Twitter experience is that you don't really know who your audience is. With blogging, for example, you might only have the vaguest sense of who's reading what you write, unless they chose to comment. But when it comes to Twitter, it's much more complicated than that. There are the people you follow and who follow you, the people who follow you and to whom you can publicly @ reply or privately direct message (and whose responses you can choose to see or not), the people reading the public timeline, and the people who might read your tweets through a badge on your blog. There are a handful of different kinds of audiences, some of which you're having a dialogue with and some of which are just watching you. Twitter fosters so many different kinds of interaction that even Evan Williams, one of the minds behind Twitter, is at pains to lay them out.

2) How Does Twitter Scale?
Even messages just 140 characters long can become an avalanche of information as your list of "followed" Twitters grows. Does Twitter need to grow beyond small networks of contacts to eventually support all the servers it runs on? In order for that to happen, there might need to be a way to sort your friends in different categories, groups, or tiers. If that happens, does it fundamentally change the Twitter model, for better or for worse?

3) What Sort of Relationships are We Building?
It's easy to joke about the shallowness of interpersonal relationships that are maintained by 140 character snippets, but I know more about some of my Twitter friends than I do with a lot of people I only know offline or who otherwise aren't on Twitter. I did a quick back of the envelope analysis of who I'm following. Of the 70 or so people, I categorized 25 under "Know a Lot," 20 under "Know a Little," and about 15 as "Fans Of." (The rest are organizations, publications, companies, etc.) What does it mean that I'm devoting equal levels of attention to people I consider friends as I am to people who don't know me from Eve?

4) What Kind of Information are We Sharing? And Who's Good at Sharing It?
One of the most interesting aspects to keep an eye on is how the way in which Twitterers fill that little text box is evolving. The original stated question that Twitter was supposed to answer was "What are you doing?" I find that the people I follow are using that question as only the loosest guiding principle, developing ideas about what's appropriate behavior as we go along and using those 140 characters to share ideas, pass along links, respond in real time to news events, and more. The open-ended questions I find particularly fascinating (but don't know how to begin to answer) is are there types of people better at sharing the info that Twitter is good at distributing?

Okay, so those are the five four most pressing questions I have about Twitter as a communications model. What are yours?

(Note: This post was edited after it came to my attention that I had only listed, in fact, four questions. One got dropped along the way. Oops.)

Back when the first rounds of web applications took off in the late '90s and early '00s, I was either in grad school or working in the non-profit/political world. I wasn't following the details of how early online tools like Blogger grew in popularity, so I'm unsure if the tremendous number of third-party tools and applications that are developing around Twitter is normal. But almost every day these days I seem to come across a new way that developers are extending the micropublishing service, either refining the core product or pushing it to do new things. I don't know if that has happened to the same extent with other apps in the past, but it is a demonstration of how at Twitter has some quite long coattails.

Twitter provides an API that opens up their app to some level of granularity. For example, after some initial tweaking, outside developers now have access to direct messaging (accessed by prepending "d [username]" to a tweet). That move created all sorts of ways for inviting Twitter users to engage with people who want to provide them with information or other services. The openness of the Twitter API have been a giant "welcome" banner for anyone wanting to make use of their platform. And made use of it, folks have -- Twitter's Biz Stone has said that the Twitter API gets at least *10 times* the traffic of Twitter.com.

Maybe the key is that Twitter is so simple: just 140 text characters zapped to a centralized server and relayed to whomever users want to receive them. They don't bring so much to the party that no one else thinks they need to bring a thing. The innovation that has been built out of it has been neat -- and instructive -- to watch.

Input Tools. When it comes to the fairly straightforward task of managing input into Twitter, any number of third-party gizmos have popped up. Desktop-based tools like Twitterrific, Twhirl, and Snitter are all engineered to the same end -- conveying your short post to the Twitter service. Where these applications are different is the options that users have to customize the fine details on how they post. Each has a unique look, layout, and feel.

Output Managers. More interesting than input tools are those that help managing Twitter's sometimes overwhelming output. TweetScan, for example, allows you to search Twitter streams and set up something similar to Google Alerts, where you get an email notification when your keywords are mentioned. Quotably sprouted up to correct what seems to be a flaw in Twitter -- responses to posts routinely get lost in the stream of messages, by organizing conversations in threads like how blogging tools like Scoop were built to accomplish. As Twitter doesn't (yet) provide users with traffic stats on their posts, Tweetburner boosts the usefulness of the service by creating custom URLs that can be embedded in tweets and then tracked. And then there's something like TweetPeek, which bundles together feeds to make the service more group friendly.

Extensions. A bevy of third-party tools exist to not just help better manage Twitter, but to grow it into something more than it is right out of the box. Twitsig, for example, takes your Tweet stream and converts it into images that can be used as signature files in forums and email. Foamee is both a protocol for indicating that you owe someone a beer or coffee and a tool for tracking who owes who drinks. But most intriguing to me is something like Qwitter, a program developed by Tobacco Free Florida. Tweet the number of cigarettes you've had in a day to the Qwitter Twitter account, and the service will keep a progress chart of how often you're lighting up. Or you can tweet in a note on your quitting campaign -- "realized tonight that it's hard to not smoke while grilling" -- and Qwitter will compile your thoughts into a journal for future reference. As a public advocacy and policy use of Twitter, that's a useful model to watch.

The powers-that-be at Twitter made the decision to create a robust API, a choice that is providing the oxygen for a thousand flowers to bloom in software development land. And it's not only plug-ins that are being developed; some of these new tools are standing in a partnership relationship to Twitter. The potential is there for many more symbiotic apps to be created, standing separate but dependent -- kinda like the many bail bondsmen who set up shop outside jails. Now the question is whether there is a business model that supports keeping the party going...

There's a real trend these days towards tying some of the advantages of the modern "web," such as it is, to actual physical spots on the planet. You heard it here first. (Hey, it was news to me when I thought of it this morning.) I started digging yesterday for something that would connect Twitter, currently my worst online addiction, to place. Twitter creates such a cloud of really touching information about people you know and want to know. But as things stand, there's no easy way to connect that data to my geographical location on the planet. That a good friend of mine is having coffee somewhere on 7th Avenue here in Park Slope is mixed in with the news that an acquaintance in Nairobi is contemplating the new power-sharing arrangement there.

I haven't managed to dig up any sort of app or tool that really ties Twitter to geography in a way that makes all that information useful to me as I go about my day. But I expect something like that is on more than one developer's drawing board, and will see it very soon.

But even in the absence of a useful geo-Twitter app, we do see on the horizon an embracing of geography as useful and meaningful. Outside.in is an online aggregator that pulls blogs in blog posts that have some sort of location information embedded or tagged. And then there's Fire Eagle. This new tool from Yahoo is still in the invite-only stage, but what it does is to collect an update on my location status from me either via the web, SMS, or third-party applications (in much the same ways that Twitter can be pinged.) Outside.in is launching a new feature called On My Radar that uses Fire Eagle to create a stream of information connected, they say, down to the very block you're standing on at the moment. And both Outside.in and Yahoo are partners in the new OpenSocial Foundation that launched yesterday, laying a foundation for a lot more of these place-tied web projects.

Of course, while I was never much into Dodgeball, that was an early attempt to tie digital info to geography. I'm not sure why it never took off. But this next round of tools is probably more welcomed today with people more accustomed -- because of Twitter, Facebook status lines, and the like -- to informing the web what they're up to on a regular basis. (Photo thx practicalowl.)

UPDATE: Ah, just stumbled upon Fireball: Twitter + Fire Eagle = Fireball. Exactly. Off to play with it...

UPDATE DOS: Carlo Scannella writes to say that Outside.in's Steven Johnson was talking up Twitter integration at a session at Parsons last week...

In March 2007, a Twitter engineer told an interviewer that he was having difficulty getting [Ruby on] Rails to handle his company's massive spike in traffic. [Rails creator David] Hansson responded by sending a heated email to Jack Dorsey, Twitter's CEO, and chastising the company on his blog for playing the "blame game" instead of solving its scaling problems itself.