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Yahoo has bought del.icio.us, which allows users to bookmark, save and share content that they tag with keywords - data that may be of use to improve search results and for ad targeting - though Yahoo says it doesn't plan, at least for now, to place ads on the site or otherwise use it for anything more than it's used now, reports ClickZ. The financial terms of the deal were not released. "We don't really have any monetization plans at this time," Tim Mayer, director of product management for Yahoo Search, told ClickZ.

"They have a very valuable community, and we want to really support that community to keep the experience as is, so they community keeps doing what they do best, which is finding great content on the web and generating data associated with that content," Mayer said.

del.icio.us founder Joshua Schachter introduced the concept of "tagging" - attaching descriptive labels to items - to online content, and many consider it a flexible and more descriptive alternative to rigid directory or categorization systems, explains Red Herring.

In March, Yahoo purchased photo-sharing site Flickr, which is built on tagging; Yahoo has integrated community elements and user-generated content across its sites, including Yahoo Local, Travel, and Shopping, and it just-launched Yahoo Answers. It introduced its own version of del.icio.us, My Web 2.0, in June, with the intention of using social bookmarks to improve search.