Hulu isn't charging for anything that they currently offer. Hulu will soon offer shows older than the ones that they currently offer, which for most shows is the last five episodes. Anyone who currently enjoys hulu, can continue watching hulu free of charge. If you want access to say, the first 5 seasons of Lost or whatever, you can get all that for $10 (at least that's how I understood it). Not really a paywall if you are paying for service above and beyond what they already offer, is it?
I honestly think this is simply Google's way to protect themselves from angry parents who want to try to sue them for Google being easy access to pornography. "You let my kid find porn on your site, I'm suing you." "Well our terms of service specifically say you have to be of legal age to use our engine, as the guardian, you are at fault, not us." etc.