The left-leaning news and opinion site The Huffington Post announced a new commenting policy to its community last Thursday.  It'll promote top commenters to regular Huffington Post bloggers. 

Community members will help determine who gets this honor by using the site's new "I'm A Fan Of" and "Favorite" links for comment and user profile pages. Paul Berry explains, "Our decision will be based on how many fans a commenter has, how often their comment is selected as a Favorite, and our moderators' preferences."

I think that this is a great idea since community driven sites need to find ways to award their members, and this is an interesting strategy.  First, commenters who earn this promotion will have to prove that they'll particiate on the site in an intelligent way.  Second, it'll encourage commenters to do their best to contribute in a constructive fashion so that they'll even have a chance to win a blogger spot on the site.  Third, promoting the best commenters is a great way to retain and encourage active participation on the site.