Sam also just tweeted that 300 YC companies are no longer around. Amazing how much transparent they are and how great YC is at picking and training. So many really crazy ideas that most would think are insane and YC is able to find the ones that make sense and help them. Seems like that's a bit less than 1/3 of all YC companies Tweet is here: https://twitter.com/sama/status/636586179970752512
What I'd like to know is the value, at exit, of the companies that have exited or gone public. Because I can guarantee you that the "valuation" of $65B+ is a totally meaningless number. This includes every single company that had a huge, unsustainable up round which will almost certainly be devalued based on future financings or exits.