This post was updated at 8:03 PM PT to provide additional comment from MoveOn.org.
Facebook issued a statement on Tuesday afternoon in response to online activist group MoveOn.org's charge that its "Beacon" advertising program is a violation of users' privacy.
"We encourage feedback from our users on new products," the Facebook statement read, "but in this case, the MoveOn.org-led group misrepresents how Facebook Beacon works. Beacon gives users an easy way to share relevant information from other sites with their friends on Facebook."
Beacon, which is part of Facebook's new social advertising strategy, broadcasts information about members' activity on third-party partner sites to their friends' "News Feeds." MoveOn's campaign has cited problems with the program ranging from its potential to reveal a user's entire holiday shopping list to the possibility that it might expose sensitive information that could put someone at risk.
Facebook's statement stressed that because this information is not public, it isn't an invasion of 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 statement explained. "Users also are given multiple ways to choose not to share information from a participating site, both on that site and on Facebook."
MoveOn.org spokesman Adam Green was quick to provide an additional response. "If Facebook's argument is that sharing private information with hundreds or thousands of someone's closest 'friends' is not the same as making that information 'public,' that shows how weak Facebook's argument is," Green said in an e-mail. "Facebook users across the nation are outraged that the books, movies, and gifts they buy privately on other sites are being displayed publicly without permission--and it's time for Facebook to reverse this massive privacy breach."