This is definitely a concern with organizations like Teach for America, where they are selecting the students with the best grades to teach at schools and eventually be responsible for creating school policy. This sort of selection has the potential to have a huge negative impact on students that are already being poorly served by the system.
With YC it's less of an issue, since it would be hurting YC itself more than the entrepreneurs. E.g. if YC is funding bad startups then it's going to hurt their returns, but if YC doesn't fund your specific startup then it's not going to prevent you from going out and being successful.
I have no doubt that Daniel is going to do an awesome job as partner. But regardless, let's not forget that it's at least 10x if not 100x harder to be a good VC than a good entrepreneur, so don't go too hard on YC. :-)