If top talent working somewhere was enough to keep top talent from leaving, then no company that employed top talent would ever loose their position without missing payroll.
You have a valid point. Top talent existed in places like Silicon Graphics, Yahoo, etc. I guess you're right, the top probably got off the sinking ship long before the rest of the crew realized what was happening.
However, I still think this event is not "bad" enough for the crew to start fleeing. This is a bump in the road. People may hate Facebook but people sure do love Instagram, WhatsApp and Oculus. Facebook has a pretty strong moat (for now at least).
