If that number is still roughly accurate, it is a pretty impressively low number. I imagine that the average percentage of fakes/bots/etc. for web services is much higher.
Actually, I think the scale is precisely what makes the number seem so low to me. It's a damned hard accomplishment to grow to 900M users while only picking up 80M fakes along the way.
80M is a large number, sure. But there are probably sites and services with 100M supposed users that have 80M fakes (some dating sites come to mind, as did MySpace in its prime). And I'm probably only exaggerating a tiny bit.
