Washington (CNN) -- Four Democratic senators called on Facebook CEO Mark Zuckerberg on Tuesday to reconsider the recent changes in its privacy settings and asked the Federal Trade Commission to streamline guidelines regarding privacy on all social networks.
"Now, users have less control over private information, and it was done without the users' permission," Sen. Charles Schumer, D-New York, said on Capitol Hill.
Schumer and Sens. Michael Bennet of Colorado, Mark Begich of Alaska and Al Franken of Minnesota sent a letter to Zuckerberg about Facebook's decision to allow third-party sharing of users' information.
Last week, Facebook began a "small pilot program" with Microsoft Docs.com, Pandora and Yelp that would offer personalized experiences when visiting those sites.
"These partners have been given access to public information on Facebook -- such as names, friend lists and interests and likes -- to personalize your experience when you're logged into Facebook and visit their sites," Austin Haugen, a Facebook product manager, wrote on the network's blog.
The senators specifically took issue with the changes because the new settings require users to "opt out" if they do not want to share any information.
"The way to go is opt-in," Schumer said. "The default position should be that the information is not shared, not that the information is shared."
Amplifying his colleagues' concerns, Schumer called on Facebook to "reverse its policy so that users have to opt in to shared data, rather than opt out."
The New York Democrat added, "The onus here should be on Facebook, not the user."
Franken emphasized the difficulty for users to opt out under the current settings, saying he would "read what you have to do to opt out, but we really only have so much time."
Bennet, who was a superintendent of the Denver, Colorado, Public Schools before being appointed to the Senate, expressed concerns about children not understanding the privacy issues.
"We want to make sure that when it comes to the very important question of privacy, that the users of these websites are in control of their most personal information," he said. "This is an evolutionary technology. There is a huge amount of benefit that comes from Facebook and companies like Facebook. But we have to be vigilant to protect the information that is in a sense personal."
Facebook defended its privacy policies in a letter to Schumer before Tuesday's news conference.
Elliot Schrage, Facebook's vice president of global communications, said the changes allow for enhanced personalization and social activity while providing users with the ability to limit who is able to view their information.
"Facebook is designed to give people the tools to control their information online and our highest priority is to keep and build the trust of the more than 400 million people who use our service," Schrage wrote. "These goals were central in the development of the new products we announced last week. Specifically, these new products and features are designed to enhance personalization and promote social activity across the Internet while continuing to give users unprecedented control over what information they share, when they want to share it, and with whom. All of Facebook's partner sites interact with a user's consent."
Schumer also called on the FTC to streamline guidelines on all social networks to allow users to easily understand privacy settings when signing up for sites.
Peter Corbett, CEO of iStrategy Labs, said Facebook's privacy policies are common among digital companies and websites.
"The onus is on the user to opt out of data collection for every major site," said Corbett, whose firm consults for major brands on digital strategy.
Corbett noted that Google collects search information and Amazon collects a detailed analysis of what books and music its consumers are browsing to recommend other products.
"Most users probably don't understand how to opt out, nor care," Corbett said. "They want an easy way to buy books on Amazon or connect with friends on Facebook. We have sacrificed privacy for convenience."
CNN has a business relationship with Facebook that allows CNN.com users to recommend and share stories with their Facebook friends. This kind of arrangement is not what the senators expressed concern about.
CNN's Evan Glass contributed to this report.