Even worse for Facebook, it's nearly all foreign people. There's just very little money to be made on the web outside of the U.S. Most other countries are either too poor or too small.
The standard of living in much of the EU is pretty bad, and in the rest there generally aren't many people. There may be 800 million total, but only a small subset of them are marketable.
The U.S. has almost as much GDP as the entire EU, while having <40% of the population which, most importantly, means a lot more discretionary income.
I hope you didn't take my statements as jingoistic, it's just a well-known fact that U.S. users monetize much better than the rest of the world in general.
