Twitter is one of the most useless progs in the whole world imo. Only useful if you've got tons of people who REALLY want to know what you're doing or are interested in your work or whatever... I'm not gonna create an account
I wouldn't go as far as to say its useless. The reason its grow to such popularity as it gives people something to do when they have 5 minutes to spare (e.g. waiting for a train). Also people like to feel that they matter and are important to the flow of the world, and blogging/microblogging gives people that.
I like microblogging, and I like Twitter. It's kind of fun finding out what the popular Twitter topics are about from time to time.