I think a MUCH better question is "Are there any companies that didn't ultimately reach exits that you regret funding: I.E. companies who you believe YC itself would have made the essential difference in their success"
This would be a company who got grew initial growth but, for lack of proper guidance and mentoring, made really bad decisions that killed them. Perhaps a company that had a chance to be huge, did well initially, but didn't have the proper connections to scale after that.
That to me is a harder but ultimately much more valuable question.
More valuable because of COURSE PG had some misses. If he didn't have misses, he wouldn't be human. But where it gets really interesting is in his estimation of the YC effect, which I think is estimable: what companies would have been billion dollar companies with the YC effect but aren't because they don't have it?
This would be a company who got grew initial growth but, for lack of proper guidance and mentoring, made really bad decisions that killed them. Perhaps a company that had a chance to be huge, did well initially, but didn't have the proper connections to scale after that.
That to me is a harder but ultimately much more valuable question.