Facebook has a built a legal surveillance machine that can read the thoughts of most people on the planet. That is very valuable. I don't doubt Facebook is incredibly valuable both for reading our thoughts and for its ability to shape them. The only current danger to Facebook's model is the EU severely curtailing their operations within the EU, but even if they have just the US market that is still hugely valuable.

Of course it is a danger to society and hugely unethical but financially they are sound.