It turns out three YC company founders used to all play in the same corporate basketball team back in Microsoft around 2004-2006! It was [redacted] and myself (RentHop). At the time we were all working on Windows Phone 6.0 and Blackberry was our biggest competitor (pre-iPhone days), so the name of our team was the RimBusters; a pretty deceiving name since our entire team consisted of short Asian guys averaging out at about 5'7". We didn't all leave at the same time though, but certainly knowing just a few other people go the risky founder route made the task seem more manageable.
Also, Lux Chen (Anywhere.fm), Anson Tsai (CardPool) and I used to all be connected on a team as well, though this one less athletic and physical, more nerdy and virtual. We were all fairly bored at our software jobs and had plenty of free time for video games. We've joked about this many times but I increasingly believe it is true: playing competitive video games might be a good test of whether someone is a suitable co-founder. Not only do you see someone's raw competitive ability and persistence, but you gain a lot of insight into how they behave and treat others during moments of stress and low morale. I also learned quickly that a person's raw ability in solo playing is not nearly as important as how well the two of you mesh as a team, hence it's better to partner up with a compatible friend than simply the most skilled person you can find. You probably think I'm over-dramatizing here but I've got an incredible number of both positive and negative data points; I almost want to do a Starcraft trial now before I ever agree to partner up with someone! Imagine a future where investors insist on your founding team reaching Master League before they will fund you.
Let's not put a subjective subset of entrepreneurs on a pedestal and lose our time gossipping about who they play basketball and go to parties with.
* figure out how to make network effects important, and
* build a bigger network than your competitors
I'm sure there are many more social connections than what is shown here too, though it must've taken FastCompany quite a bit of sleuthing to unearth at least this much.