These acts of apparent philanthropy from ridiculously wealthy people rub me the wrong way. It feels like those rich patrons from older times who would bestow their "generosity" as they pleased, except that in modern times most countries have frameworks in place to make this sort of work happen, and these rich people choose to ignore them, or worse, disparage them.
Companies like Facebook (and people like Mark Zuckerberg) actively avoid paying taxes whenever they can, in a lot of countries that, for example, have public healthcare and other public institutions that would normally benefit from these taxes.
It's a bit like repeatedly stealing some kid's lunch, and then making fun of the kid for her weakness while appearing strong (and stronger in comparison to the weak kid) and compassionate when the kid passes out and you carry her on your back.