Getting excited about the marketing and lead-generation possibilities of Facebooks' new features? Not so fast.

Lawmakers and privacy watchdogs are asking the social networking giant to rein in recent changes that extend the social network's tentacles into partner websites, making it more difficult for users to limit personal information that gets shared beyond their networks. 

On Tuesday, the U.S. Senate jumped into the fracas, with Senator Charles E. Schumer, the New York Democrat, calling the changes a betrayal of users' trust. Along with three other Democratic senators – Michael Bennet of Colorado, Mark Begich of Alaska, and Al Franken of Minnesota – he wrote a letter to Facebook founder Mark Zuckerberg asking Facebook to reverse its decision to share user data with third parties (like you) unless users first go through a multi-step process to opt out. (Schumer and Co. want users to have to "opt in" to the feature instead.)

"Social networking sites have become the Wild West of the Internet," read the senators' letter. "The innovation they represent is welcome but users need to have the ability to control their private information and fully understand how it's being used."

Schumer, the Senate's No. 3 Democrat, said in a Capitol Hill press conference: "They've created here, inadvertently, a gold mine of data for unsolicited ads, spam and even scammers." On Sunday at 5:13 pm, Schumer updated his Facebook status to say he was asking the Federal Trade Commission "for guidelines to be established for social networking sites, like Facebook, on how information can be shared or disseminated to third parties." The senator also named MySpace and Twitter as causing concern. (For the record, Schumer appears to have tried Twitter just once: To send a missive Nov. 19, 2008 saying, "Just joined Twitter!" Not that he claims to be a social media expert—at the news conference he said he learned about Facebook's latest changes from his daughter, who's in law school.) 

The Electronic Privacy Information Center, a privacy watchdog group, also announced it was preparing to file a complaint with the Federal Trade Commission. The group wants closer scrutiny of how Facebook uses the data it has gathered from its 400 million users—and for clearer privacy guidelines for all social networks.

A Facebook spokesman responded that the site already gives users unusual control over their data and that it only shares what they have agreed is for public consumption.

"Our highest priority is to keep and build the trust of the more than 400 million people who use our service,"  Elliot Schrage, a vice president at the company, said in a letter to Schumer. "We welcome a continued dialogue with you and others because we agree that scrutiny over the handling of personal data is needed as Internet users seek a more social and interactive experience."

Facebook's response didn't mollify Schumer, who proclaimed it inadequate and said his staff planned to meet with the company. (In a statement Tuesday, Facebook said it hoped to meet with members of Congress to "alleviate any concerns they may have.")

The Federal Trade Commission also will have its say. "Our plan is to develop a framework that social networks and others will use to guide their data collection, use, and sharing practices," Jessica Rich, deputy director of the FTC's Bureau of Consumer Protection, told the Associated Press. (For his part, Schumer promised to introduce legislation to expand the regulatory agency's reach over social networking sites if the FTC doesn't think it has the power just to require what it thinks is appropriate privacy controls.)

Greg Sterling, an analyst for Internet consulting and research firm Sterling Market Intelligence, told the AP the scrutiny for Facebook is "a metaphor for their rise to power."

"Facebook has something approaching half a billion users," he said. "It's such an important site — probably second only to Google — even on par with Google." Stay tuned.