Polished Coins

Tom and I were discussing polished coins today and it reminded me of this video I came across recently.

Would you want that coin?  The poster mentions numerous times that this should not be tried on valuable coins, but what would you think if you saw a silver dollar shined up like that?  Are there any circumstances this would be permissible?

To be honest, I found myself visibly cringing as I watched that poor Kennedy being abused.  Should coins ever be cleaned?  I would love to see some sort of exhibit on cleaned coins on display at our coin show in May.