> Even if your answer to this is "Well maybe there shouldn't be any public infrastructure in the first place", it simply shifts the problem somewhere else: if a private company would be managing the infrastructure, rest assured they would also ask for usage costs..

I wouldn't say there shouldn't be public infrastructure. For the last part, though, mightn't Facebook consider charging the company managing infrastructure for the ability of their customers to access Facebook? I think people would be a lot less likely to subscribe to an ISP that didn't facilitate access to Facebook.