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Report: Clearspring acquires bookmarking service AddThis

AllThingsD reports that the widget company has bought a start-up that does only one thing: aggregates all those "Bookmark This" buttons into one.

Kara Swisher at AllThingsD reported Tuesday that widget-maker Clearspring has acquired a start-up called AddThis for an undisclosed price.

Swisher referred to AddThis as "the top bookmarking and content-sharing tool on the Web," a title that comes from numbers from traffic firm Hitwise. Basically, AddThis is a company that makes little buttons that publishers can put on their blog posts, articles, or what-have-you to aggregate the ubiquitous bookmarking services into one. It pulls in the Yahoo-owned Delicious, Google, Microsoft's Live Bookmarks, Firefox, Furl, and a bunch of others.

The company already has its buttons on Web sites from Fox, ABC, WebMD, TechCrunch, Entertainment Weekly, Glamour, and CBS, which publishes CNET News.

What's in it for Clearspring--especially since AddThis doesn't generate revenue? Executives told AllThingsD that having those buttons distributed all over the Web will be valuable for analytics and (in one way or another) ad revenue.

This post was updated at 9:11 PM PT on Thursday to clarify the source of AddThis' market ranking.