If it was only YouTube... I recently got the prompt on GMail after a login, it was a mini-tab inside GMail for quite some time, it's a recurring question or even requirement on any new Google service, but the closest I've come to converting my old-style Google account into one with a G+ profile is certainly when adding your account on Android. One touch-sensitive button to start the process directly next to the one for skipping it..

Quite the obstacle course.