They got a lot of criticism before and immediately after their IPO for not justifying their value. Today they are genuinely making a lot of money. Their advertising platform it is valuable not unlike Google's. I think the only thing likely to harm facebook is losing users.
Which is supposedly happening.
The more people flirt with quitting, the more they realize their feeds have been reduced to attention whores and babies (their real friends stopped posting long ago), the mroe they'll quit and it'll just snowball.
FB messed up by getting too big. I'm going to post my true thoughts when my grandfather might read them? Nope.