For the record: my guess as to why he left Yahoo? Because he was offered CSO of Facebook.
My impression has been that alex wants to tackle problems that are large in scale. Probably less about money and more about doing good for the most people possible.
And I worked with Chris Rolf, who is frighteningly good.
all i can say is that in very happy. while he did a little real good at yahoo, he was mostly doing two things: promoting his name and adopting everything in sight based on cool factor without regard for hard facts.
life for people that actually know things was hell. life for the frivolous i-just-read-about-some-cool-thing-on-hn was paradise and full of bonuses.
Especially amused by the attempted "read-something-on-HN" snark. Yeah, that's where all the high-profile elite security people are these days. Hanging out on HN with me.