Faced with mushrooming anger over his company's handling of a new advertising system called Beacon, Mark Zuckerberg, Facebook's chief executive officer, issued an apology.

"We've made a lot of mistakes building this feature, but we've made even more with how we've handled them," Zuckerberg said. "We simply did a bad job with this release, and I apologize for it."

Facebook "missed the right balance" with Beacon, Zuckerberg said. "At first we tried to make it very lightweight so people wouldn't have to touch it for it to work. The problem with our initial approach of making it an opt-out system instead of opt-in was that if someone forgot to decline to share something, Beacon still went ahead and shared it with their friends."

"It took us too long after people started contacting us to change the product so that users had to explicitly approve what they wanted to share," he added. "Instead of acting quickly, we took too long to decide on the right solution. I'm not proud of the way we've handled this situation and I know we can do better."

Late last week, the company had detailed changes to Beacon. Still, things worsened on Friday after Facebook lost a desperate legal fight to prevent 02138, a magazine about Harvard, from publishing documents relating to a lawsuit against Zuckerberg that accuses him of stealing the idea and code for Facebook from three Harvard classmates.

The crisis came just weeks after Zuckerberg antagonized many Facebook users and others by telling the Foursquare conference in New York, "There is no opting out of advertising."

Over the weekend, the tech blogosphere decided enough was enough. This post, from Russell Shaw, is indicative of the surly mood.

Today, according to Zuckerberg's statement, Facebook released "a privacy control to turn off Beacon completely." But the damage may have already been done.

The incident illustrates that even a 23-year-old as brilliant as Zuckerberg is having trouble running a company that is growing rapidly and coming under increased public scrutiny. Should Facebook, valued at $15 billion thanks to a recent investment by Microsoft, decide to go public next year, as has been speculated, it is almost certain that the company would first bring in a more experienced executive to replace Zuckerberg as C.E.O.

Zuckerberg, of course, would still be expected to play a major role. Chief Social Grapher, perhaps?

The question is, who would take the C.E.O. job? Facebook needs its own Eric Schmidt.