Great new service for searching comments and commenters on the web: Backtype.com.

BackType is a service that lets you find, follow and share comments from across the web. Whenever you write a comment with a link to your website, BackType attributes it to you. We give comment authors a profile featuring all the comments they've written on the Internet. If you don't have a website to use when you fill out comment forms, sign up and use one of ours.

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http://www.backtype.com/