For one thing, how likely are we to see another gruesome collision between Facebook's need to make money and its users' privacy? Beacon -- the company's ill-conceived and poorly received attempt at tying advertising to user behavior -- may be a thing of the past, but there's no indication that Facebook has given up the way of thinking that led its management team to even consider Beacon a viable idea.

Consider the immense pressures the site's facing. It doesn't have a fully fleshed-out revenue stream, and money, while it's so far been plentiful for the company, still doesn't grow on trees.

At the same time, Facebook has two tremendous resources. First, it's got its skyrocketing popularity: The site surpassed 222 million users in December, according to comScore.

Second, if my family's, friends' and colleagues' usage habits are any indication, it's also growing every more integrated into our daily lives. Normal adults -- and not just us Internet types -- can talk in public about events that transpired that day on Facebook and not seem weird.

With such strengths, and confronted by such heavy demands, it may be too tempting for Facebook to say no to the next Beacon. Would users rise up a second time?

In the meantime, we ought to celebrate what Facebook's accomplished as one of the champions of what we call Web 2.0. Along with peers like MySpace and Friendster, it dramatically remapped what we thought of as online interaction. With sites like Twitter, it got us sending, responding to and thinking about contacts' near-real-time status updates. And following the lead of Salesforce.com, it's attempting to remake itself as more than just a task-oriented Web site: Instead, it's trying to become a platform for all manner of Web apps. We'll keep watching on that one.

We're living in a more interconnected world thanks to Mark Zuckerberg and company. In some ways, the rise of Facebook has helped fulfill the promise of what the Internet was all about: Easy, instant connections and closer communication. But its success thus far may yet pave the way for new challenges in how we balance privacy and profit online. And there's no telling whether this milestone will mark the start of new worries we've yet to consider.

For the time being, however, Facebook's helped to reshape how many view and use the Internet, and for that, it deserves a hearty congratulations. And a very happy birthday.