Numbers:
- Facebook Monthly Active Users = 2.4 Billions
- Facebook Fake Users, not included in MAU = 3.4 Billions (FB declared recently disabling that much)
Total: 2.4+3.4=5.8 Billions

Worldwide internet users: 4.3 Billions

Maybe a little function like this could help?

function createFBAccount() {

if (numberOfAccounts++ > peopleOnEarth) {
print "You are not human"
exit
}
...
}