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).
If Apple has top tier talent, why do they ship an OS with a huge security vulnerability? With a map framework that has memory leaks? With a messaging app that messes up the order of messages?
If Google has top tier talent, why did they create an OS that allowed a third party developer to siphon calls, contacts and messages?
If this is your argument, then no company has top talent.
Also swooping all kind of privacy data, like call logs, messages, contacts, calendar info is from management. Engineers really know better that this will be found out sooner and later, and then it's the end.
How certain is this? Whether you like what Facebook does or not, you can't deny their engineering talent is top tier. I don't even use Facebook but I'd still want to work there just to work with the people there and the environment. Companies like Facebook and Google are pretty engineer friendly, more so than other companies. I don't think this event will be the tipping point for top talent to leave Facebook.