"People use it" is a pretty important feature for a social network though.

Whatever replaces Facebook will have to be "cool" enough to get people to actually want to use it. "Facebook but with better privacy" just isn't cool, so the average person isn't going to bother.

Orkut and MySpace were both a lot larger than when Facebook started. Facebook did some great things and innovated during their early years. But yeah, nowadays they can just coast by being marginally better than any new product.