From what I've been able to gather, teens prefer creating "ephemeral" less-curated content in favour of throwing up "permanent" posts to Facebook (for all/too many to see) until it's past its use by date. So in a sense, they may or may not be more conscious of being seen by their parents who are mostly tech-savvy (compared to past generations anyway).
So if what I just wrote is somewhat true, the commonality between Cambridge Analytica and teens preferring Snapchat to Facebook is actually privacy or lack thereof (perceived or otherwise).
As for mass exodus - Hotmail, MySpace, Flickr, Yahoo... Where does one draw the line - is Facebook invincible?
I believe that more people care about privacy than they themselves realise. It's only a question of how much it'll take for patience to be tested. Keep in mind that easy-technology (the iPhone) has only been around for hardly more than 10 years; a lot of "non-geeky" people are still learning the ropes of how to balance their digital and physical lives.
Also don't forget that this is only one piece of bad news that Facebook has had of late. We're still wondering how useful online advertising really is, and how often it's gamed by ad click-fraud, etc. Aside from that, I can't comment on where FB's share price might be at any future point from now; not that I should even care.
Edit: With reference to big companies and which ones can eventually fail, I recommend reading Benjamin Graham's "The Intelligent Investor".