With Bell, standard oil and past monopolies... the goal was to decentralise while keeping oil and telecom viable. We wanted what they made, and didn't want disruptions.
Do we want what FB makes? Is it scarce? I feel like we would have a sufficient supply of likes, shares, messages and posts regardless. There doesn't need to be a $trn company for those to be supplied.
Generally, I think the issues at stake have evolved. Many of the problems with today's monopolies are power related, rather than efficiency related. I think FB is enormously inefficient, but this is kind of besides the point.