> Aren’t those reasons to weigh the company’s views more heavily?
No. Coming back to the environmental (which is decent metaphor, I think), a company which dumps into the local river is going to fight tooth and nail against any regulation that stops them from doing this because it might have a significant effect on their bottom line, while for most people this will not be enough for them to care to get involved because the harm is difficult to measure individually and hard to conceptualize (but, over the entire population, has significant detrimental effects). This shouldn’t mean that the government should weigh corporate concerns more heavily.
> The cost benefit (the potential gain from a cleaner environment versus the potential loss from reduced economic activity) is different for the US than for other countries.
Well, of course it is: it depends on which countries have business that rely on their negative externalities not catching up to them.
> Legislators must of course balance the resulting input
The problem is that the input legislators get is from a source that is strongly biased towards viewpoints that have a lot riding on the laws being put in place, which is generally not the people you want to be listening to for a fair, balanced opinion.
> If the benefits from increased privacy don’t outweigh the losses to companies like Facebook, the law is a bad one.
This is highly dependent on which group you are looking at. From Facebook’s perspective, most privacy laws are bad for them, while from their user’s perspective most privacy laws are probably good. The issue is that the latter group is being left out when this consideration is made, or at least is not well represented.