How would you break them up?
All you could do for Facebook is to require them to divest Messenger and WhatsApp. I can't really see how Facebook could be broken up beyond that in any reasonable way.
Google would be a little easier, splitting search and Android would not damage either but the advertising behemoth would be two smaller behemoths, who would now have to compete with each other.
Not arguing for this, I think it is a bit early to be concerned with "break them up if you ever want innovation again". Microsoft wasn't broken up - barely touched in fact - but Ballmer's sheer incompetence caused them to miss out on advertising, social networking, and mobile, allowing Google, Facebook and iPhone/Android to create huge new markets that are nearly 100% Microsoft free. Here's hoping for a Google and Facebook version of Ballmer to take over the reins when the founders decide to move on...