I've posted about Twitter for writers here on Midlist Writer before. I feel it can be a useful tool as long as you know what you want to do with it and stay focused. So far I've been pretty successful at keeping a good signal-to-noise ratio in who I follow, but I just had to unfollow someone for the first time.
I won't mention names in order to protect the guilty. Suffice it to say it was a feed that had a Civil War title and a bio saying the guy tweets on topics related to the American Civil War. At first he did, but as time went on more and more political commentary slipped in alongside the history links and battlefield news. For the past couple of weeks all he's been doing is spouting Nobama stuff. He hasn't said Obama is a Muslim, but I have a feeling that's coming.
Now it's totally within his right to criticize the president. What bothers me is that his Twitter feed claims he's going to tweet about the Civil War. I don't like being misled. If you want to be successful on Twitter, be open about what you're going to do. Otherwise you'll start losing followers.