Here's another more controversial topic.
I've always wondered by using your nails or picking the seam was morally less desirable than using spit and rubbing to shine the ball. To me they seem like equal but opposite processes; one is to preseve shine and the other to destroy it. So why is one considered ball tampering and the other not?
As far as doing stuff to the ball, I reckon you should be able to do anything to the ball you wish as long as you don't get any outside help from a bottlecap or Vaseline etc. Because if you stuff-up the roughing up of the ball, it's to your detriment and you have to live with that.