At the top of every page you'll notice a new Featured Member Comment. This is a display (partial if it's too long) of a thumbnail+link to the associated video along with the author of the comment. The selected comment is that which has received the most votes in the past 12 hours.

So, umm... Yeah.

[update]
We've changed it so it will effectively feature once every five minutes a random <= 12 hour old comment with at least 5 votes.