Timeo Danaos et dona ferentes, which roughly means "Beware of Greeks bearing gifts."
One doesn't build a multi-billion company by giving things away.
Exactly, FBStart is no charity, so why do they do it? You don't even need to integrate your product with FB. I would love to apply but the offer is too good to be true.
Maybe a modern version: beware of geeks bearing gifts?
The saying is almost 2000 years old [1], so I think if somebody wanted to modernize it they've had the chance :P