But market forces only work well when there's a lot of competitors. Facebook, on the other hand, is very close to being a monopoly — and just like relativistic speeds break classic mechanics, just like that the monopoly status breaks the classic market forces. And they should decrease the amount of freedom the company enjoys as well.
Of course, there's a question about how we define "monopoly": there's a lot of counter-arguments to this, and a lot of them perfectly valid. There's Twitter, there's self-hosting, there's all these forums around the internet... But at the same time, isn't it strange that "monopoly" as we understand it is a binary category? I think it's reasonable to think about it as a continuum; and Facebook today would certainly be very far on that axis.
Every time I meet a new acquaintance, we add each other on Facebook. If I tell them about my music project, they search for it on Facebook to like it. If I go to a party, I search for the Facebook event, and so on. After disabling my Facebook account for half a year, it became painfully evident that I wouldn't be able to keep in touch with a lot of family and friends without it. Of course, it's their voluntary choice — but at the same time, depriving a person from access to this website could seriously decrease his quality of life. It's not just commercial product that you can choose to use or not anymore; thanks to the network effect, it's a necessity.
And a commercial entity that becomes so essential to everyday life should not enjoy the same freedom in wielding the ban hammer as "some website on the internet".