The social networking juggernaut Facebook turns five years old today, and the chatter online about the birthday ranges from congratulatory to cautionary.

Yes, the site has grown to over 150 million users strong, but no, the site hasn't yet figured out how to monetize its friendship with the world and resolve that oh-so-awkward tension between being seen as both a trusted shepherd and a revenue-seeking schleper of our personal data.

However, regardless of where the money comes from, there's no denying that social networking has become a major force driving the attention economy online. Our latest report on social networking shows that 35% of internet-using adults now use the sites, and older generations are starting to nip at the heels of the young networking digerati.

And while it's hard to imagine that there won't be another application that comes along to lure us away from the glow of Facebook, it's also difficult to imagine today's users abandoning such a vast and valuable archive of their social interactions in favor of starting with a clean slate somewhere else. At the end of the day, while few of us have paid any money to use Facebook, many of us are heavily invested in it.