UPDATE 2: A spokesperson for Senator Michael Bennet tells Fast Company that Facebook representatives will be meeting with Senator Schumer's office soon. The spokesman could not go into the breadth of such potential government regulation, nor did he comment on what would occur if Facebook did not comply with the senators's demands. "[It's] just a starting point," the spokesman said. "We need to see what the FTC says."

UPDATE: At a press conference on Facebook privacy concerns (see the previous update below for a full description), Senators Bennet, Schumer, and Franken joined together to condemn recent changes in policy that make user data available to the public, whether through 3rd-party aggregators or targeted advertisements. During the conference, the senators argued that it was unfair for Facebook to automatically enroll users in the "state of sharing," and urged Facebook to make it so, by default, user data is private unless members choose to opt-in.

"They've created inadvertently a public gold mine of data for unsolicited ads, spam, and even scammers," said Senator Schumer today. "It's unclear to the user what information is being shared, how it is being shared, and whether they have the ability to keep the information private, and that's why we sent our letter to Mr. Zuckerberg."

"Let's say you shopped at a grocery store for two years, and without your permission, the grocery store sent a list of everything you purchased and made it public," Sen. Schumer said. "There's certain things you might not want people to know, and it would be wrong to do that, and it's wrong to do this."

"It's just really hard to opt out," Sen. Franken chimed in, criticizing Facebook for changing its policy "unilaterally" without asking its members. "This is a consumer protection issue."

Senator Schumer stressed that Facebook should put a "premium on privacy," and made clear that even if Facebook goes along with their suggestions, that the FTC will still set up rules to protect people's privacy.

It's unclear what breadth such FTC rules would have on the Web, but in a question over whether such regulations would affect other sites known for privacy issues (e.g. Google), Senator Schumer bluntly said, "policies have to be developed." He continued, "You know a violation when you see one," in an apparent ode to Potter Stuart.

All three senators appearing said they would consider legislation on the issue if the FTC did not have jurisdiction, and even if Facebook addressed all their concerns. "The default should be to opt in," Sen. Franken concluded.

Previously: It looks like consumer protection is coming to Facebook. In a letter sent Tuesday to Mark Zuckerberg, the founder and CEO of Facebook, four senators expressed concern over the social network's user privacy.

"The expansion of Facebook--both in the number of users and applications--raises new concerns for users who want to maintain control over their information," read the letter, which was signed by Senators Chuck Schumer (D-NY), Michael Bennet (D-CO), Mark Begich (D-AK), and Al Franken (D-MN). "Providing opt-in mechanisms for information sharing instead of expecting users to go through long and complicated opt-out processes is a critical step towards maintaining clarity and transparency.”

The senators took issue with user profile data being available to the public, and they also questioned Facebook's policy to allow 3rd parties to store user information indefinitely. The senators heavily criticized the new instant personalization feature, which enables certain Web sites to mine user data to customize advertisements.

The letter comes a day after Sen. Schumer asked the FTC to examine Facebook's privacy policies.

"We believe users should have more control over these very personal and very common data points," the senators wrote in the letter. "We believe Facebook can take swift and productive steps to alleviate the concerns of its users."

We will update this post throughout the press conference scheduled for noon, and we expect a comment as well.