Update: PayPal has contacted The Register via its PR agency to point out the reason that the destruction of goods exists in its terms and conditions. "The reason why we reserve the option to ask the buyer to destroy the goods is that in many countries, including the US, it is a criminal offense to mail counterfeit goods back to a seller", we are told.
How does it make sense that it´s illegal to mail counterfeit goods back to the seller?
Because you give him a chance to try again. Which in a way makes you an accomplice. If I was selling fake Gibson guitars on eBay and all that could happen to me would be buyers returning their goods to me, now THAT would be a business.