That's very interesting, I would be curious to know on average how much their seeds have returned so far, is the "1 startup out of 10 is a success" valid also for Y-combinator?
They've published some numbers in the past (http://tcrn.ch/1d1iB8Y) but this new move could be because they think they are missing from not being involved in later stages of rgeir own startups and those that weren't not accelerated by them.