The deal will further help sate advertisers who are mostly stuck with user-submitted content, suffering from numerous issues ranging from unprofessional production to potential copyright violations. Although this may be seen as an overall successful move for keeping the site alive, there's something they might be missing here. YouTube was built and still primarily thrives on videos uploaded (legally or otherwise) by individual and unpaid users.
There's no reason why this deal would curb that – users certainly aren't going to stop uploading – but it might begin to dilute the site's content. Could it be an indication of a shift towards professional videos as opposed to user-created ones? If Google's motivation is purely profit-driven, professional content certainly has more potential to bring in cash. I doubt YouTube's user base wants to see it morph into a Hulu clone, but it seems like a possibility to me.