Yeh, he is all set. But any signs that Facebook is hemorrhaging both users and ad revenue it good. Zuckerburger will always be all set.
You are not thinking logically on this. The more people that sign up for FB and do NOT click the ads, the more money it will cost FB in data stream costs. He's gotta' pay for the data coming into and out of his pipe. He makes up for it with click-through ads. So if everyone simply stops clicking the ads, he gets nothing, but spends more. Net negative revenue after expenses.