Facebook founder Mark Zuckerberg apologized to the site's users in a blog post on Wednesday for the way in which controversial new ad feature Beacon was rolled out last month and promised that users can now turn off the program if they want to. "We've made a lot of mistakes building this feature, but we've made even more with how we've handled them," wrote Zuckerberg of the program, which tracks the online activities of its users on other Web sites and sends that information to their friends.

But after more than 50,000 users signed an online petition complaining that Beacon was invasive and could broadcast information they preferred to keep private, the company announced last Thursday that it would make the warnings about the program more prominent. Then on Wednesday, Facebook released the feature users had asked for: a privacy control that can turn Beacon off completely.

"We simply did a bad job with this release, and I apologize for it," Zuckerberg said. "While I am disappointed with our mistakes, we appreciate all the feedback we have received from our users. I'd like to discuss what we have learned and how we have improved Beacon."

The company's founder explained that Facebook had wanted Beacon to be simple enough to let users share information across sites with friends, but lightweight enough to not get in their way as they browsed the Web.

"We were excited about Beacon because we believe a lot of information people want to share isn't on Facebook, and if we found the right balance, Beacon would give people an easy and controlled way to share more of that information with their friends," he explained. The mistake the company made, he admitted, was that in making Beacon an "opt-out system instead of opt-in," so that if someone forgot to decline to share something, Beacon still went ahead and shared it with their friends. In the end, he said, once Beacon was rolled out on November 6 and people started to complain, it took Facebook too long to find the right solution to users' complaints.

The program has apparently backfired from an advertising standpoint as well. According to The New York Times, Facebook has been meeting with advertising agencies over the past few days to discuss their concerns about Beacon. The original plan was to sell ads alongside the messages sent to users' friends about their purchases and visits to other Web sites, but some ad agencies reportedly expressed surprise that Beacon required users to take action to stop the messages from going out and said they didn't want Facebook to push its users into Beacon against their will.

"I'm not proud of the way we've handled this situation," Zuckerberg wrote, "and I know we can do better."