Facebook has expanded a feature that allows users to integrate their accounts across the Web.

Facebook Connect allows members to log in to partner Web sites, track friends' visits to those sites, and update their own Web site activities on their profile pages. The feature aims to make it more convenient for Facebook members to access other sites by using one login. Facebook announced this week that it's adding more partner sites in a bid to expand the service significantly.

Facebook announced Monday that it will encompass more sites, including the Discovery Channel, Digg, Twitter, Evite, Socialthing, StumbleUpon, the San Francisco Chronicle, and Geni. The feature will increase Web traffic for partner sites if Facebook users -- who number 120 million -- are drawn by the universal login system.

Although it's unclear how Facebook and its partners will profit from the arrangement and split revenue, the insight into members' behaviors will support behavioral advertising. It's also likely to add to privacy concerns.

However, the social networking site has promised more caution in terms of protecting user privacy than it has granted in the past. Facebook was heavily criticized after launching its Beacon advertising program last year because users complained it infringed on their privacy and did not give them enough control.

Facebook reacted to the backlash by giving users more control over what information is shared and with whom.

Facebook Connect launched in May. In addition to the advertising benefits it provides, the feature could encourage some Web sites to incorporate more social features and user interaction.