Damn, I keep missing people's (and communities') posts on LJ/DW! I can't really figure out why, either. They have both slowed down enough that it should be easy to click through a day's posts.
I think part of the part of the problem may be the behavior of the things I have as feeds on the two sites. Sometimes they won't post for a day or two, and then they'll dump a lot at once. The result is I'll be flipping through my reading list/friends feed and hit something I know I've read already, and then I'll stop. And in some cases, I've read it already at the source blog or site itself (like Scalzi's Whatever) instead of on LJ/DW.
I'm going to try to do a better job of combing though these things more carefully. I keep missing beta requests on Fan Grammarians as well as posts on things like the Weiss v. Saiyuki writing challenge comm.