I found myself explaining Twitter to my best friend, an architect in New York City, who despite being worldly, erudite and smart, was completely at a loss as to why he should even care about Twitter, much less incorporate it into his crazily busy life.From my friend's perspective, Twitter is yet one more intrusion into his personal space, one more means by which people will break into his train of thought to demand his immediate attention, demand immediate action, demand an immediate response without giving him the time to think a problem through. "Isn't this demand for more, faster, immediacy part of the problem with our society?" he asked.

But everyone is Tweeting these days: President Obama, Sarah Palin, John McCain, the Baltimore police department, even the freaking Pentagon. Heck, Hugh Jackman is offering $100,000 to the non-for-profit that Tweets him with the best 140-character pitch. Some guy who just started following me has more than fourteen thousand followers -- and follows that many himself. You have to ask yourself -- what the heck for?

It's gotten to the point that there's even a business helping people find available Twitter handles.

My friend isn't alone in his assessment -- apparently Twitter's retention rate is a lamentable 40% -- and Nicholas Carr pithily says, "Twitter may turn out to be the CB radio of Web 2.0."

InformationWeek's editor in chief, Rob Preston, notes that businesses seem to be looking for excuses to implement Twitter, rather than finding actual reasons.

Most enterprise users of social apps have jerry-rigged an ROI, mostly around cost savings and productivity improvements, but those justifications are still mostly qualitative. Meantime, skepticism abounds.

But Twitter has a lot going for it, beyond fast communication capabilities. For one thing, it is hardware- and software-agnostic; you can "be" on Twitter on any device, anywhere you can get online. It is simple to use. You can see what people are talking about in a big old hurry. You can also figure out what people are saying about you or your company. TechCrunch founder Michael Arrington tells BusinessWeek,

I realized that in the last two months a subtle shift occurred: I now need Twitter more than Twitter needs me... It is now an important part of my work and social life, as I carry on bite-sized conversations with thousands of people around the world throughout the day. It's a huge marketing tool, and information tool. But it is also a social habit that's hard to kick.

Sometimes you're found guilty by association, and it's tempting to do so with Twitter when Michael Arrington, the ultimate in solipsistic tech journalism, gets in on the act.

So are we all talking to each other in a collective circle-jerk? Perhaps, but if that circle gets big enough, it stops being an echo chamber and starts resembling something like a societal conversation. Finding out what Tweeters are thinking about and telling them about yourself becomes relevant to a larger crowd. It's not fifteen minutes of fame -- it's 140 characters of pithiness (if you can manage).

Let's face it, the telephone used to ring obnoxiously, haranguing us with its loud, persistent clanging bell to pick up the receiver in the middle of the night to bring us news we'd just as soon have learned in the morning from the mail or telegram. You might have wanted to stop it right there in its tracks, but you couldn't, any more than you could stop the railroad from cutting through your town, bringing the world to your doorstep.

There are lots of reasons why Twitter matters and why we Tweet. But in the final analysis, we Tweet because it's there.