If someone still has any doubts about the value of YC, they should read this email exchange. PG is pushing for the startup as if it was his own. He genuinely wanted them (and also the VC firm) to succeed. Great stuff.
What? He was invested in them. Do you think he wants to see them crash and burn?
More prosaically, if you can delay the company's getting to break-even, they'll need more rounds of investment, which mean you can buy more of the company.
And then, of course, there are personal feuds. Remember what happened to Scout Electromedia? Their shutdown probably had as much to do with investors being pissed off about being ignored as with any actual rational assessment of their future prospects.