Facebook will reveal a new ad unit in coming weeks that will appear within the social networking site's recently launched, and controversial, News Feed feature, a self-updating list of alerts indicating when a user's "friends" make changes to their pages.

The new ad unit, called Sponsored Stories, will occupy the third position within a News Feed, either as a small banner-like placement or as a video clip, writes MediaWeek (via MediaBuyerPlanner). When users click on the ad, the user's entire network of friends is alerted, and they can then interact with the ad. According to Facebook, the ad will allow advertisers to harness the site's social-networking dynamic and leverage social-networking behavior.

Facebook has also generated publicity for opening its site to any internet user. Previously, users had to have a college or university email address to join the site. The new policy, launched on Sept. 26, resulted in the fastest growth of any single day in the site's history.