Han, I agree it would be interesting to know how many tubes are actually created by people.  The vast majority of those that actually have content are automatically created through Ditto.  And, since most of the rest appear to be artist related (as opposed to fan/user related) but come with no content and no attempt ever appears to be made to add content or in any other way modify the tube, I have to think that they are also being generated automatically somehow, as well.