Seems like a good move for Quora. They'll get early access to acquihiring super talented folks at struggling/failing startups. At the least, they can generate goodwill and word of mouth as a good place to work. Talented people know talented people, etc.

Not sure about the impact on YC though. It may create an environment of mixed incentives. Quora's incentive is almost perverse, in that they get the most value out of YC from failing startups.