I guess, as a theoretical computer scientist myself, my first reaction is to roll my eyes. I get that these guys are trying to drum up interest with investors/funding agencies, but "My greatest fear is that my research is too successful" is still pretty grandiose. It sounds like those physicists who thought they had figured everything out in the '30s (or AI researchers before the last winter). I think it's pretty telling that Zuckerberg isn't worried despite having an empire built on AI - he's not asking anyone for money.