There is a greater impact to society than measurable direct impact to users. Facebook should be liable for their total net externalities, divided by the probability of being caught for such actions. That is the economic premise of the FTC. This should include fines and remedies for anti-trust violations as well, and since this is an opportunity cost, it does scale with the size of the company.
In fact you should probably subtract the direct costs to users, as there is already a mechanism in place for collecting damages, and any government intervention on this axis should go to something reminiscent of a victim's fund.
In fact you should probably subtract the direct costs to users, as there is already a mechanism in place for collecting damages, and any government intervention on this axis should go to something reminiscent of a victim's fund.