Do YouTube videos buffer for offline playback on Google's iOS app?
Yes, assuming you don't quit the YouTube app after it loads. You can also do this with the YouTube website; play a video, it starts loading the video with a QuickTime-like player, and you will see it buffer. If you start playing the video in the Safari and exit Safari (while it's still in the background), you can double-tap the home button to bring up the audio controller and hit Play.