I see you have some downvotes but I came here to say the same thing. Zuck is using the birth of his daughter to advertise a new venture.
You want to be generous? Great, do it!
Telling us in a letter to your daughter as a hook to attract eyeballs is kind of weird and exploitative.
Update: I also thought I should say that this is no big deal, he has some different ideas about what's ok and what's not and I see that every day, I'm not mr perfect either.
I guess the reason it's interesting in this case is because he is head of facebook and entrusted with a lot of people's personal information. If his judgment is different to mine then I don't feel comfortable entrusting him with my social life.