Facebook's newest features may make it easier to share with family and friends across the Web, but it seems not everyone wants to be an online social butterfly.
Last week, the popular social networking site unveiled a round of changes meant to make the Web more social and personalized, by expanding Facebook's presence to other sites.
On thousands of sites, including ABCNews.com, a "social plug-in" now lets users "like" content and see what their Facebook friends have liked, directly from those sites.
On three sites piloting an "instant personalization" feature, a user's profile information and friend list are automatically read by the site and used to shape the user's experience. On music site Pandora, for example, you can see what your Facebook friends like to listen to. On Yelp, you can see which restaurants they've reviewed.
But in recent days, some of those data-sharing changes have drawn criticism from Facebook users, privacy advocates and, most recently, federal regulators, who say Facebook needs to give its more than 400 million members more control over the personal information they disclose on the site.
"With great power comes great responsibility and sites like Facebook have great responsibility," Sen. Charles Schumer, D-N.Y., said Tuesday at a news conference on the issue. "In my view, it ought to be the user who determines who gets what information, not Facebook."
Joined by three other Democratic senators, Schumer sent a letter to Facebook, urging it to revisit its new policy and make it easier for users to control and protect their privacy.
One of their top concerns was Facebook's "opt-in" policy, which means that personal information is automatically shared with some partner Web sites unless the user goes through the process of disabling this feature.
"Grocery stores don't tell everyone what groceries you're buying and Facebook shouldn't tell everyone what your interests are, unless you want them to," Schumer said.
In addition to sending a letter to Facebook, Schumer asked the Federal Trade Commission to create guidelines for Facebook and other social networks to follow.
Calling the Internet the "Wild West," he said it was "utterly confounding" that almost no rules govern a Web site as massive as Facebook.
In a letter responding to the senator, Facebook said it takes privacy very seriously and that its new products give users "unprecedented control over what information they share, when they share it and with whom."
Facebook spokesman Andrew Noyes said, in an e-mail to ABC News, "We appreciate the concern raised by Sen. Schumer and expect that further dialogue with interested members of Congress about the user controls that accompany the tools announced by Facebook last week will alleviate any concerns they may have."
But privacy advocates point out that this is not the first time Facebook changes have triggered privacy concerns. In 2007, when Facebook unveiled Beacon, which tracked user behavior on other sites and shared the information on Facebook, user dissatisfaction was so strong that Facebook ultimately backpedaled and CEO Mark Zuckerberg apologized.
In 2009, the social network announced another set of privacy changes, which again sparked complaints from privacy advocates and Facebook users.
"It shouldn't be a full-time job adjusting your privacy settings on Facebook," said Kurt Opsahl, a senior staff attorney with the Electronic Frontier Foundation. "It would be nice to see Facebook not only change to an opt-in model where people have control over who gets what information but makes some real promise that that should continue to be the case."
In addition to the opt-in policy, Opsahl said that one of his key issues is the personal information Facebook now considers public.
It used to be that Facebook users could list their interests, activities and other similar information in their profiles and set limits on who could see them (from only certain friends to everyone).
But under Facebook's new system, information users list under "Likes and Interests" in their profile automatically connects them to a Page and lists them on that Page, and that information is now considered public. If you list your college and work information in the provided profile boxes, that information also connects you to public Pages.
Let's say you list pandas under your "Likes and Interests," even if you limit who can see that when they visit your Facebook page, you're still publicly listed on a Community Page that aggregates all people on Facebook who like pandas.
The only way to keep interests, activities and other personal information private is to include it in the bio section of your profile page, Facebook said.
In a blog post explaining the new Pages, Facebook software engineer Alex Li said profiles no longer include "boring" static text listing likes and interests.
"Now they are a living map of all the connections that matter to you," he said.
But though Facebook says the pages are meant to enhance online communities, EFF's Opsahl asked, "How does it advantage you the user to be one of the 3 million names listed on the cooking page?"
"It's too much information for ordinary people to look through. The people advantaged by it are data miners and advertisers," he said.
Opsahl also said it worried him that Facebook is moving away from a system that only let partners store data for 24 hours, to a system that lets them store data indefinitely.
"What that means is that you have to trust these applications or these Web sites -- not only trust what they are now, but what they are ever going to be," he said.
On Facebook blog posts explaining the new changes, scores of Facebook users have expressed their unease with the changes. Last week, social media blogs noticed a Facebook status message instructing users on how to opt-out of the features sweep the site.
But Adam Ostrow, editor-in-chief of social media blog Mashable, an ABCNews.com partner, said that the user reaction to these changes has not been as negative as responses to previous changes.
Though some users have complained about the changes across the Web, he emphasized that members have not yet opted for a popular protest tactic -- Facebook pages denouncing the changes.
"From what we're seeing, it doesn't seem like a backlash anywhere near the proportions of other times Facebook has tried to push the envelope on privacy," he said.
While the new changes make a couple of pieces of data more public, they don't dramatically change things, he said.
Given how many partnerships Facebook has forged and the clear investments it's made in the new features, Ostrow said, "I don't see a way for them to undo it... I don't see them really back-pedaling from the open graph and all these new features."
And analysts say that a more open Facebook is just what marketers are hoping for.
Debra Aho Williamson, a senior analyst for eMarketer, said marketers are keenly interested in what people say and do and reveal in the social Web, but it's traditionally been very difficult to access.
"It's a wealth of information. Marketers would love to tap into that," she said. "Facebook is making the first step toward that."
When people make purchases, she said, data shows that they are almost always interested in the opinions of family members and friends. So integrating Facebook information with other brands' Web sites could help users make important shopping decisions, she said.
But, she added that depending on the kind of site, users might not want to reveal their own preferences or habits to everyone in their Facebook network.
"Sharing has become a public activity. ... I think consumers are being more open about what they want to say about themselves more publicly," she said, but added, "I don't think people are less concerned about privacy."
And, ultimately, she said, Facebook's success depends on how willing people are to share their information with not just their network friends -- but everyone. And that remains to be seen.
"I'm not sure the general public is fully aware of it and using it," she said. "So far, it's really on early days."