You may now get anonymous comments that are spam. The most recent one I saw claimed "I added you as a friend, add me back" with a link marked 'my journal'. It was actually a link to a yahoo webcam.
First off, why would you leave an anonymous comment if you were a registered user, asking to be simul-added? Sheesh...anyway, give serious though to turning off your anonymous comments. AT the very least, make sure your IP tracking is on...that could be useful for tracking down where this crap is coming from.