Wait, people are reading my bio?!? (JK)
Yes, I do like to hang out on Twitter. For each of my books, I schedule Tweets every few hours for the first couple of days to announce a release. I don't tend to do a ton of promotion on either Twitter or Facebook, though my Facebook interactions lean more toward promotion because I find it a total time-suck. The same could be said for Twitter, but I manage my time on there. Plus, it's very social/interactive, so I get a lot of support from fellow writers, editors, etc.
Social networking sites can be helpful, but they shouldn't be the sole focus of your promotional efforts. I do a LOT of promo, but as far as I've heard it's not obnoxious because I spread out where I'm doing it - Twitter, Facebook, my blog, guest blogs, chats, giveaways, blog hops, etc.
Does that answer your question?