I do. Frequently. If it's an inappropriate comment, I delete it. A conversation with another commenter that has nothing to do with my post? I delete it. (ETA: It has to be way, waaaaay off-topic for me to do this.) If it's a threadjack, a mommy-jack, a woe-is-me-jack or similar? I delete it. It's my wall. If they want to post this stuff on their own walls, they're more than welcome to. If they whine and complain about my deletions or commit these annoying acts once too often, I delete them from my friends list. I don't spend a lot of time on Facebook, I don't want to have to deal with people who need all attention on them at all times.