The cosmos knows IPOs and employees have windows, so I'm surprised by the extent of the sell-off. I see this as exaggerated "accumulation-distribution" ... so the only question remains for the trader to find the divergence in price from this "false" sell-off to the beginning of the accumulation process. Will $20 suffice? That's certainly good enough for me to be buying "nickel" calls that survive long after the employee window opens and closes.
I still see FB as a $100+ trade ... even Suckerberg can't alienate himself from a billion people before FB finds ways to produce revenue (a phone, an app, some ads ... bingo ... : )