I find this one (Facebook) really fascinating and hard to judge, but am not as optimistic as you about their chances. It will be interested to see how they make the transition to a company with broader revenue streams. I compare with myspace as they depend on fickle consumers posting content and don’t have much of a moat IMO.
At present they are bleeding users, particularly young ones, they’ve been hit by many privacy scandals, their revenue depends in advertising which can dry up very quickly (as we saw in the dotcom boom), so I think they’ll have a hard time adjusting, particularly if there is a quick crash in the tech market which craters their revenue, but you may be right, they might be able to stay alive and grow via acquisitions.