Why is the US always focusing on individual companies instead of working on laws to protect them from all companies invading the privacy of their citizens? Banning one player isn't going to help much in the long run I would think. Edit: I am an EU citizen if it matters.
People can only inhabit a finite number of social media networks, and there can eventually only be a fairly small number of big players in a position to produce massively detailed rich profiles on individuals and therefore hold most influence on them (consumer behaviour & voting behaviour)
Imagine that the USA clamps down heavily on facebook, and in 4 years some rival company from Russia or China ended up achieving the largest market share / richest per-person psych profiles. That represents a security threat even greater than the (nearly catastrophic) threat that Facebook represents today. Who wins and who loses in this race is going to make a massive difference in what the planet looks like 20, 10, even 5 years from now.