• by Wendy Davis , Staff Writer @wendyndavis, May 11, 2010

Facebook has spent the last several weeks touting its controversial instant personalization program, which automatically shares users' names, photos, friend lists and other data with Yelp, Microsoft Docs and Pandora.

As it turns out, however, Facebook isn't placing all of its users in the program. The company confirmed to MediaPost today that new members are excluded from instant personalization -- which Facebook describes as a pilot program.

Facebook so far hasn't answered questions about why it's not including new registrants in the test, so it's difficult to draw conclusions about its intentions. Still, one would think that with all of the scrutiny given to Facebook and, specifically, to instant personalization, the company would have made clear from the beginning that it wasn't planning to roll out the feature to everyone.

The main reason the program is so controversial is that it operates by default: Logged-in users -- some of them, anyway -- who visit Yelp, Microsoft Docs or Pandora automatically share data with those sites. Users can opt out, but then their data can still be shared through their friends. The only way to prevent that is for users to individually block the three companies from retrieving data.

That system has been criticized by everyone from U.S. senators to consumer advocates to tech writers, who argue that Facebook is violating users' expectations by sharing their data without their explicit consent.

That's not even the only flaw in the program. A researcher found that a security hole in Yelp was leaking Facebook users' data, TechCrunch reports. While that hole was quickly fixed, the incident still highlights just how vulnerable Facebook can make its users by sharing their information.