BackType, as you likely already know, offers not just the ability to follow people (like me) on the site, but you can also set up keyword alerts to get updates by e-mail when the topics are mentioned in comments online, and you can even see trends of these keywords over time.
Since signing up for FriendFeed about 16 months ago, I've logged nearly 8,000 comments (about 500 a month, apparently), so for BackType to tap into this rich content archive will be beneficial, not just for the FriendFeed power users, but for those who want to improve the monitoring of social media. BackType, one of my favorite new services of 2008, has stepped up its game and gotten even more useful. You can follow my activity on BackType here: http://www.backtype.com/louisgray.