I've been using Twitter for a while now. "Using" doesn't quite seem like the correct verb though.

I've been... participating? No - that's not entirely right either, as I mostly just follow the (often mundane) updates posted by people in my friends list; I haven't been contributing all that much myself.

I've been... watching Twitter, I guess.

Twitter is built on the central premise that your friends around the world are interested in the answer to the question posed by the site tagline: "What are you doing?"

Hmmmm. I think when my friends are using Twitter as a kind of "micro-blog" (posting tiny nuggets of interest, pointers to breaking news or stories they've found online) then, sure - that can be interesting and useful. I first heard about the Virginia Tech shootings through a comment posted to Twitter.

As for the "just hopping into the shower" or "making a nice cup of tea" posts (or - excuse me - "tweets" in Twitter vernacular), well - those I can probably survive without.

I'm staying plugged in to Twitter, though, as the intensity of this always-on, presence-driven world fascinates me. Joe Jaffe, in a recent "Across The Sound" podcast made some really interesting points about the potential of Twitter and the like as "real-time marketing" vehicles. (See! A podcast I like! They're not all tripe).

Twitter posts are now being indexed by the omniscient Google, apparently. This prompts Jaffe to float the idea that big brands need to be carefully monitoring the Twitter feeds (and Jaiku and Dodgeball and all the other Twitterish apps) as another line of instantaneous reputation monitoring.

As an example, a lot of people seem to post updates to Twitter from airport departure lounges - often updates of the "XYZ Airlines sucks" variety, when someone has been parked in that same departure lounge for the last N hours. Smart marketers might be well-advised to watch for, and be prepared to respond to, breaking reputation leaks through services such as Twitter.

And while we're on the topic of airline departure lounges, the latest vowel-deprived Web 2.0-y app to suck me into its elegantly Ajax-ified embrace is Dopplr (thanks for the invitation, Suw). To quote from Dopplr's "About" page:

"How does Dopplr work? It lets you share your future travel plans with a group of trusted fellow travellers whom you have chosen. It also reminds you of friends and colleagues who live in the cities you're planning to visit. You can use the service with your personal computer and mobile phone."

The service shows you a timeline of your travel plans mapped against those of your friends, so you can arrange to hang out in far flung locales, months into the future.

So now my friends can be constantly kept up to date not only on the prosaic minutiae of what I'm doing every day, but also where I am, where I'm going, and where I've been. If I opted to start posting to Twitter as often as some of the real addicts out there, anyone following my feed would soon know more about my workday existence than even my family do. More than any entirely sane person would ever want to know.

It's utterly fascinating, but all rather odd. How long before someone mashes up a few of these services, hooks into the GPS on your mobile phone, and releases Stalkr - the ultimate always-on, Web 2.0, presence-based, real-time, nano-blogging, social software, FOAF-tracking tool?

Again, I'm hugely intrigued by where this stuff is going, but every now and then it feels like we're all signing up to wear ankle tags.

Super groovy Ajax-based ankle tags, for sure, with names like Anklr or BluTag (that one really exists, btw) - but I wonder if we'll find, as Martha Stewart did, that they start to chafe after a while...