They already know how. Its not difficult for Google or any other provider to disable unauthorised playback devices/apps. Adobe already have a DRM streaming system for FLV and SWF verification to stop you from accessing something without the official player. Thats not to say that you can't, just that its harder to do and starts a game of cat & mouse if you really want to do it which will cause issues with the DMCA in the US if you do.