Sounds like a "focus" issue - they're not going to want you to be dividing your attention, especially not with something they're not involved in.

<<I do not actually have 4 facebook apps. I do not actually have 1 facebook app. I do not actually have any hacking skills, but occasionally think about becoming a hacker, applying to YC, and creating useless Facebook apps. Please indulge me by answering my made up questions.>>

No thanks.

If they are part of the corporation YC funds.

So does one recommend putting all your projects in the corporation of YC funds?

One probably recommends focusing on one project at a time.

P.S. If you ever get rich, I expect an email rubbing this comment in my face ;)