I actually can't say I know exactly. I think I've had that account a year maybe two and just started using it a couple of months ago. I don't really see it as all that, though once in awhile you can have some fun with it. Some people love it......rumor has it Jenn Aniston Broke up with John Mayer cuz he is a twitter addict - that just passed by my reader from mashable....so silly.
As Katie rightly said, Twitter is fun only if you've a large number of friends on it. I've figured a geeky way to auto update my twitter through friendfeed. It automatically updates my twitter account taking feed from facebook, my blog, posterous, flickr, picasa, goodreads et al.