Marc andreessen family

The key to investing, Andreessen contends, is to be aggressive and to fight your instinct to pattern-match. “Breakthrough ideas look crazy, nuts,” he said, adding, “It’s hard to think this way—I see it in other people’s body language, and I can feel it in my own, where I sometimes feel like I don’t even care if it’s going to work, I can’t take more change.” Andreessen believes that the major barrier to change is sociological: people can embrace only so many new ideas at once. “O.K., Google, O.K., Twitter—but Airbnb? People staying in each other’s houses without there being a lot of axe murders?”

A16z passed on Airbnb’s A round in 2009. Reid Hoffman, the Greylock V.C., who led that round, and who is a friend of Andreessen’s, said, “Once something like Airbnb gets going, Marc can get a very good sense of it, of the economic system—but he’s not necessarily as good at the psychology of why it would get going in the first place.”

Brian Chesky, Airbnb’s co-founder and C.E.O., told me, “In 2011, when we were starting to get some traction, Marc and Ben did a one-eighty and were very hum

•