Moderating of users
I spoke today about serial posters, I realise that in an ideal world you want as many posts from as many people as possible, so stifling serial posters is counter productive. So how about this as an idea.
You limit the view of the posts to the other people looking. By this I mean, rather that seeing 1 person posting 20 questions in a row, you break this up and only show say 5 posts from that person in a row.