A 4% effective tax rate has a lot more to do with investment in R&D, declaring losses in accordance to the tax code etc.
The optics are terrible, agreed on that.
Regarding your first question, its not about how much value I get out of Facebook, since I'm not paying $160 for it, advertisers are paying for the ability to reach people.
Let’s not pretend that Facebook isn’t ALSO involved in a lot of “technically not illegal but clearly unacceptable to the majority of society” tax avoidance strategies.
They aren’t unique in this sense but it’s just loophole after loophole and is the kind of thing that is at this point a textbook example of failed corporate/ social responsibility.
The optics are terrible, agreed on that.
Regarding your first question, its not about how much value I get out of Facebook, since I'm not paying $160 for it, advertisers are paying for the ability to reach people.