We have a much higher threshold for startups that have already been through an "accelerator" program. Mainly because we expect them to have thereby been accelerated; if they're not doing well, we worry they might be unacceleratable. It's also a problem that such startups will be twice as diluted at Demo Day, which decreases their fundraising options.

I can think of two startups we've funded that had been through things calling themselves "accelerators" before YC.