I would think that the type of person who would succeed in the startup world is one who would come up with an ad-hoc idea in order to do a startup, rather than the type of person who wouldn't do a startup because they couldn't think of an idea.
I've been involved in a lot of companies, I can code, do (simple) multi-layer PCB layout, server-admin, tons of real-world business experience, can go in cold to a group of hundreds of people and present almost any topic and manage positive or negative audience feedback under pressure.
I have an idea (submitted in the past, denied, still working on it though)... But, YC might frankly have a BETTER idea for me. Or together we might be able to identify an exploitable market.
I see this as kind of YC's version of an EIR, and frankly I think it's cool and will likely produce several successful projects.
Anyway, it's an interesting experiment.