This is important.
I dont know where the line is, but we should agree that a line is needed.
People are saying a line is not necessary. That is at the core, the problem. We need to agree that these companies -by accident or otherwise- have become a common good, similar to a "utility"
Take a similar example: at some point a company stops being a company...and becomes a monopoly. Where is that line? We dont know. However its important we recognize private companies operating as monopolies are not in the best interests of society.
Private companies operating as common goods providers should be subject to additional rules. That is what we should agree on. Then let others define what that is.