-- Access to advice from more experienced people (in many respects: programming, architecture, business model, user acquisition, usability, user experience. It's rare for any startup to have 2-3 founders that together are rock solid in all these areas)
-- A name-brand incubator that helps you attract talent
-- A name-brand incubator that helps you attract high-value first adopters
-- Networking with other very talented YCombinator applicants and alumni
-- Plenty of news coverage from tech pundits and other journalists because of the YCombinator brand
I would bet you that the overwhelming majority of YCombinator applicants do not apply for the money. They most likely apply for all the other intangible benefits.
I'm sure somewhere in that statement is a cogent opinion about downside of accepting equity investments and the loss of control entailed, but the lack of structure and general ranting makes it hard to see.
Some people won't get anywhere without the network so who are you to tell them to not follow their dreams because you don't want them to Sell Out.
Last time I checked most Start ups can't wait to Sell Out to someone...