Facebook's new ad program has taken some heat from the site's users of late, with some of that ire now concentrated at a MoveOn.org Facebook page designed to petition the social network to "stop invading [users] privacy!"

According to a report in The Wall Street Journal, the MoveOn.org page, which launched yesterday, attracted nearly 2,000 members overnight.

Facebook launched its new ad program earlier this month. Using behavioral targeting, the program tracks user activities on commercial pages within the site and on sites outside of Facebook, alerting the friends of users via News Feeds of actions taken in connection with certain pages.

While critics charge that the program violates user privacy and is difficult to opt out of, Chris Kelly, Facebook's chief privacy officer, disagrees.

Kelly, who pointed out that users have several chances to opt out, called the MoveOn.org-centered backlash "fairly muted."

The new ad program also has raised some legal concerns. Less than a week after Facebook announced the program, a law professor pointed out that the practice may run afoul of New York's privacy laws. Facebook denied any legal wrongdoing.