[marvin]

I think the real issue is that when Facebook didn't hire him, he went on to found a competing company which Facebook felt compelled to pay 16 billion for. That's a big cost.

[gohrt]

If FB hired him, then one of the other N messaging apps would have become the biggest one, and Facebook would have bought that company.

[crassus]

That value may never have been created otherwise. If the acquisition turns out successful then not hiring him may absolutely have been the right thing to do, even in hindsight