I have to ask: do people really believe that "2 billion users" claim?

I live in Europe, and yes the majority of people I know have an account, but nowhere near all of them, and they're often unfrequent users. But more importantly: with the places where FB is banned, all of the people too young to be on it, all the people too old to have an interest, and all of the people who have in general a limited/difficult Internet access and have more important things to do than get facehooked? Being told that 2 out of every 7 human being manually created their account and are 'active users' who log in at least once a week (or is it month?), somehow leaves me skeptical.