The second Google purchases Hulu, the site's content licenses will be revoked by All the providers and they'll demand a renegotiation of far more favorible deal.

Hulu was only able to stay afloat because it was backed by FOX NBC and Disney, and got all those shows at a heavily discounted price. The networks were very cautious to not create an iTunes for TV that would grow to be too big to control, they use very restrictive and short term content license to ensure that.