NEW YORK — In Facebook's vision of the Web, you would no longer be alone and anonymous. Sites would reflect your tastes and interests — as you expressed them on the social network — and you wouldn't have to fish around for news and songs that interest you.
Standing in the way is growing concern about privacy from Facebook users — most recently complaints that the site forced them to share personal details with the rest of the online world or have them removed from Facebook profiles altogether.
Facebook responded to the backlash Wednesday by announcing it is simplifying its privacy controls and applying them retroactively, so users can protect the status updates and photos they have posted in the past.
"A lot of people are upset with us," CEO Mark Zuckerberg acknowledged at a news conference at Facebook's Palo Alto, Calif., headquarters.
The changes came after Facebook rolled out a slew of new features in April that spread its reach to the broader Web. Among them was a program called "instant personalization" that draws information from a person's profile to customize sites such as the music service Pandora. Some users found it creepy, not cool.
Privacy groups have complained to regulators, and some people threatened to quit the site. Even struggling MySpace jumped in to capitalize on its rival's bad press by announcing a "new, simpler privacy setting."
To address complaints its settings were getting too complex, Facebook will now give users the option of applying the same preferences to all their content, so that with one click you can decide whether to share things with just "friends" or with everyone.
For those who found it complicated to prevent outside websites and applications from gaining access to Facebook data, there's now a way to do so in a couple of clicks.
It's not clear whether the changes will quell the unease among Facebook users, which has threatened to slow the site's breakneck evolution from a scrappy college network to an Internet powerhouse with nearly a half-billion people.
"They've lost the users' trust. That's the problem," said Marc Rotenberg, executive director of the Electronic Privacy Information Center, an advocacy group. "In the earlier days, there was time to regain it. It's not so clear now. I think it's getting more serious than making changes and moving on."
Some of Facebook's loudest critics offered cautious praise but indicated the young company will need to do more to prove it cares about privacy.
Sen. Charles Schumer called it a "significant first step that Facebook deserves credit for," but added he'd still prefer that Facebook require users to actively turn on sharing with outside sites, rather than having sharing be the default setting.
For some users, the problem has been that the company has changed its privacy settings so often that keeping up with them became too much. Before Wednesday's announcement, Craig Mather, a 28-year-old graduate student in Portland, Ore., was already complaining of having to adjust his privacy settings every time Facebook comes up with a new plan.
"It puts us on our guard, where we feel like we are trying to plug a leak," he said.
For Facebook, being seen as a company people can trust with the personal details of their lives is key. Users will only share information if they have control over who sees it.
"The kernel of what we do is that people want to stay connected and share with those around them," Zuckerberg said.
Jules Polonetsky, a former AOL executive who now co-chairs the Washington-based Future of Privacy Forum, said the privacy concerns stem from Facebook's transformation from a place to socialize with friends into the "de-facto identity system for the Web." It's a big step. Facebook is no longer just a place to share photos and play "Mafia Wars." It's a reflection of who you are online.
Facebook has touted its culture of authenticity from the beginning. It asks users to go by their real names on the site, and it deletes obviously fake profiles.
Zuckerberg described his vision for the Web in April with "an old saying that says when you go to heaven, all of your friends are there and everything is just the way you want it to be." He challenged software developers, entrepreneurs and others to make "a world that's that good."
Facebook's lifeblood is advertising. It makes money by letting businesses target ads to specific types of users — such as 30-year-old single men living in Brooklyn who are interested in motorcycles and yoga.
Zuckerberg, who turned 26 earlier this month, says his vision is not about the ad dollars. He was 22, he said, when "Yahoo and Viacom and all these companies" were clamoring to buy Facebook, offering $1 billion or more. For a 22-year-old to pass that up might be kind of crazy, he acknowledged, but he said it shows "it's not about the money."
Even so, convincing people that sharing more is good for them has at times been an uphill battle. Users revolted against Beacon, a feature that broadcast people's activities on dozens of outside sites when it launched in 2007. Facebook gave people more control over Beacon before scrapping the program completely as part of a legal settlement.
More recently, Facebook has come under fire for a security glitch that exposed some users' private chats, and another that revealed users' information to advertisers in a way they could identify them, going against Facebook's own terms of service.
For Luke Finsaas, who is 24 and has been using Facebook since college to keep in touch with friends and family in Australia, whether the site's vision works out in the end is a matter of trust.
"It's incredibly brilliant but wildly terrifying," he said. "Google has been around for a while, and we know that they are pretty serious about privacy and protecting us. We know that they've got our back. But Facebook has had privacy issues in the past."
Google Inc. has struggled with its own privacy issues — most recently with its Buzz social media experiment and, particularly in Europe, with sending cameras into cities to take photos for its Street View map feature.
But users feel a deeper connection with Facebook, where they exchange not just messages and 140-character tweets but news of major life events and newborn baby photos. That means privacy concerns are heightened, too.
"Facebook wants to be the social center of the Web, and any social interaction that takes place on the Web they want to be in control of," said Debra Aho Williamson, a senior analyst at research firm eMarketer. "If its plan succeeds, that could be a big problem. They will have access to too much information."