Yeah, I never use my twitter unless I'm at one of the trips or conventions where people I am working or traveling with tweet schedules and all their movements. I'm not really big on facebook or blogging either.
I think part of my trouble with twitter is that none of my friends use it. So, I'm not sure "who" I'd be talking to. Which is probably a good thing because most of my twitter followers are businesses and business contacts so I'd need to self-censor anyway. I used my twitter account last month because I wanted to test ReadUps and turns out that was the first time in over a year and a half I had used it! (I use assorted Hootsuite, Taptu, and other lumpit all together social media things that let me read what everyone I'm following posts or if I have the rare something I want to post out everywhere).
Ah well mine are all people in the book community. Publishers, authors, other bloggers, readers of my blog. I don't police myself AT ALL! I just say whatever. Yes I sometimes drunken tweet myself into trouble :D I can understand why you wouldnt use it much if it was just a business tool. :)
I spend a lot more time reading twitter than using it. My problem is that with 140 characters you aren't given enough background to fully trust links. So my list of trusted people, yes, those I'll read links from. But anything retweeted that won't let me see the source code of the links? I usually don't trust. Twitter's useful in its way, but people don't often realize how the lack of context can be ify.