I started following blogs to read and comment. Then I started blogging. The same thing might happen with twitter, though I don’t know how often I plan to update. It certainly will make the small number of feeds I started following in the last few weeks a bit easier to read.
It’s funny, I signed up for Facebook a couple of months ago but don’t think I’ll ever do much with it (last sign-in: a couple of months ago) except accept the occasional friend request. But twitter is less demanding and has more of a public character; I’ll probably end up using it more than I expect.