I have a Twitter account. I don't follow anyone. (Technically my wife is marked to follow, but she doesn't post, so it doesn't really count.) I don't sign in, and I don't "tweet." The very thought of Twitter is just distasteful to me. I'm very aware that this is not a popular opinion. Twits all over the interworld tweet their day away, follow their four thousand Facebook friends, and know exactly what their five favorite celebrities are doing every ten minutes.
Without being a twit myself, I feel a little presumptuous talking about it. Maybe it isn't really fair to criticize something you haven't tried, but if I really believed that, I wouldn't be able to advise you not to set yourself on fire, and how dare I refuse to do drugs.
I base my dislike of Twitter on two things. One, the vast majority of "tweets" that get tweeted are inane, pointless trash. I love Nickelback's music, but I don't know them personally, and I don't care what time they go to bed, what they ate for breakfast, or which if them is fighting over some groupie chick. I definitely don't want to know about Ozzy Osborne's stomach flu. (Got to lay off the bats, man.) However, at least part of that is our society's obsession with celebrities, which I also don't grok.
My other problem with tweeting is that this service is encouraging our society to communicate in 160 character messages. We already have problems teaching people to communicate in complete sentences. This is only going to compound the problem. There have been numerous studies about tv watching and how it impairs the development of people's attention spans. The same thing is happening with language. Twitter is contributing to the degradation of our ability to communicate well.
I do realize that not every Twit falls into these traps, but so many do, that I don't get the appeal.