This is an interesting thing over at Life on Mars: Comment Icons.
Post a comment, supply the URL to your blog, and if your blog has a locatable RSS feed which points to an image, that image will be displayed next to your comments. As I've been known to have a mild obsession with LiveJournal, this reminds me a lot of the usericons in use there, only distributed across blogspace, which is what I've wanted to see done for a long time.
All the infrastructure of LiveJournal, Friendster, and the like could be recast as distributed feeds and metadata, with smarts on blog servers or personal clients. One piece at a time...shortname=comment_icons