It has been on YCombinator's front page for 2 days and promoted by Stripe: https://news.ycombinator.com/item?id=8114901
That's a lot of publicity and attracts a huge userbase. Not saying there are no fake accounts. One would have to buy phone-verified FB accounts combined with a lot of manual work to make large amounts of Stellar that way, though.
No doubt, just saying that 75000 accounts =/= 75000 people. I'd bet 1/3 atleast is fake.
Also there are FB account "bot"-nets that are used for upvoting and liking on FB. Those can claim those stakes too. (I have no verified phone and was able to claim)