Backtype is a new service that helps you to find, follow and share comments. it aggregates comments from the blogosphere at one place, you can search comments and people.
When you post comments on various sites using your Blog URL and your name, they will be aggregated here at one place. Each commentator will get a profile name at backtype, you can see all your comments at your profile. You can claim your comments by signing up to backtype, and you can also follow people by searching by their name.
If you find an interesting comment, you can share it with others by emailing them, it provides links to the original comments and for replying to those comments.
It is a good service for searching through information on particular topic to find out what people are saying, but i am not sure how far it is useful for users.