1) I've been thinking about doing this. I try to only perform 1 or 2 "have you seen this post?" queries per page load, otherwise I start to take a pretty severe performance hit. I might be able to swing something, though.

2) I worry about wasted space. Ye olde idkfa did this, and it worked out OK, but I felt that the extra inch or whitespace (blackspace?) just made for more lines on the screen.