If Facebook were a country, it would be the third largest ... in the world. It reminds me of Nebraska, where Husker Stadium became the third largest city in the state on game days (at a meager 80,000 something). If Facebook were a country, would it have an anthem? Would it have a flag? Would its president be Mark Zuckerberg? It's a weird thing to think about. But it also creates some kind of fusion, of people the world over. It's like we really do exist under a single set of dictates. The Facebook Constitution (aka the terms of service and privacy agreement).
Anyhow, here's a fun updated Map of Online Communities by the folks at xkcd.com on the current landscape of the interwebs. Click on it to make it huge. I highly recommend this, because you'll see all the funny and quirky details.