Asked the same question on Quora [1]. Adam D'Angelo's answer:
There are a bunch of reasons why it's valuable for Quora to be a YC company:
>>We'll have Sam and all the other partners to help us.
>>We get to be part of the YC community / alumni network of founders.
>>We get access to all the resources of YC.
We were raising money anyway, so there was no overhead in letting YC participate. And independent of the benefits to Quora, I think it will be fun personally to participate in some of the YC events. I hope my perspective can help some of the other companies.
There are a bunch of reasons why it's valuable for Quora to be a YC company:
>>We'll have Sam and all the other partners to help us.
>>We get to be part of the YC community / alumni network of founders.
>>We get access to all the resources of YC.
We were raising money anyway, so there was no overhead in letting YC participate. And independent of the benefits to Quora, I think it will be fun personally to participate in some of the YC events. I hope my perspective can help some of the other companies.
[1] http://qr.ae/y2vdI