Liberal advocacy group MoveOn.org launched a campaign yesterday against Facebook’s “Beacon” advertisements, which transform member transactions on third-party partner sites into product/service endorsements and insert them into their friends’ “news feeds.” Facebook members, or should I say “fansumers,” are automatically opted-in to the program, and while they are offered the chance to opt out, they can do so only on a case-by-case basis.

MoveOn considers that to be a glaring violation of privacy and has launched an online petition protesting it. “Facebook users across the nation are outraged that the books, movies and gifts they buy privately on other sites are being displayed without permission to lots of people–and Facebook needs to reverse this massive privacy breach,” MoveOn.org spokesman Adam Green said in a statement. “They should respect privacy by switching to an opt-in process like most other Facebook applications, not opt-out–which was solely designed to benefit corporate advertisers.”

Facebook, of course, says it’s not violating anyone’s privacy. “Information is shared with a small selection of a user’s trusted network of friends, not publicly on the Web or with all Facebook users,” the company said in a statement. “Users also are given multiple ways to choose not to share information from a participating site, both on that site and on Facebook.”

Of course they are. But as Forrester’s Charlene Li notes, they’re easily missed and don’t give users nearly enough control over their behavioral data. “The biggest problem is the lack of transparency,” Li explains. “Facebook is right in that I would really like to have some things that I do on third-party sites to conveniently appear in news feed, e.g. events I’m attending from Evite or eBay/craigslist listings so that my friends know about them. That’s the promise of Beacon. But I need to be in control and not get blindsided.”