They make $200/year per user in North America, all 250 million of them. Cut that to 1/3 and their value as a company is far lower, but they still make more per user than a subscription service like Netflix. Now, you can say "nobody thought that ARPU was sustainable", but they have a long history of making unbelievable numbers bigger.

Their real mistake was not pushing to own the entire vertical stack, building unassailable moats like Google and Apple. Oculus is that bet, and other companies like Valve are pursuing similar strategies.

On a 3 month chart FB is down 10% from start to now.

That's hardly "epic".

And the NASDAQ composite is down 13% in the same time frame.

Everything is going down right now. -10% over the last 3 months doesn't seem that epic to me.