So what happens here, exactly? Say John Doe is picked without an idea. What does John do during his YC time? What does YC get a piece of in return, exactly?
On another aspect of it, the negative reaction of some, I think there may be a subconscious message that this makes it more about what someone has done than is doing or will do. That probably threatens some folks a bit, even if it doesn't practically make any actual difference to their chances.
Idk, I imagine someone in YC without an idea would work just as hard if not harder than, say, someone who already has a product with some traction. I imagine John Doe would wake up every morning thinking "crap, I'm already behind everyone else! I better get moving" (and he'll have to get something together for demo day, which presumably is what YC will get a piece of).
I'm sure this is impossible to generalize, but I wonder if in some circumstances it might even save people a few weeks of time. If a lot of teams change their idea during YC, presumably in some cases it takes them a while to decide (or to be convinced by the partners) to do so. Whereas if they go in not attached to any particular idea, it might be easier for pg & crew to talk them out of their bad ideas so that they reach a good idea more quickly.
On another aspect of it, the negative reaction of some, I think there may be a subconscious message that this makes it more about what someone has done than is doing or will do. That probably threatens some folks a bit, even if it doesn't practically make any actual difference to their chances.