This isn't a new problem though. Anti-trust laws have been enforced previously without a strict definition.

"Although the courts "have not yet identified a precise level at which monopoly power will be inferred"[1]

[1]Section of Antitrust Law, Am. Bar Ass'n, Market Power Handbook 19­20 (2005).

I kinda fundamentally reject the premise here. When I say that a sandwich is "too expensive", I don't mean that there ought to be a law against selling sandwiches for that price.

The context is dealing with the problem of the existence of a too powerful company. Dealing with a too expensive sandwich requires no laws.

If refusing to work with a company is impossible, it's a monopoly, right? Otherwise, you are free to respond to the too-powerful company the same way you respond to the too-expensive sandwich.

If a company is using its power to do something harmful, write laws against the harmful thing, irrespective of how much power the company has. Illegalizing shadow profiles of non-users would be a good step forward, illegalizing them only for FB-sized companies would be less good.

If a handful of companies are operating as a monopoly, that's already well-defined as an oligopoly.

I think the only other situation where a company can be too powerful is if they get too much power over the regulators. I expect it's rare to get there without becoming a monopoly or oligopoly, but it's probably not impossible.

>If a company is using its power to do something harmful, write laws against the harmful thing, irrespective of how much power the company has.

I agree, hence my explanation of why there are no laws against "too powerful" companies. It is not an actionable condition.