eBay Rule 1: Don't be a fucking idiot

I recently put a laptop up for sale on the ever more expensive eBay. A few days after the listing had started I received notification from eBay that my listing had been cancelled by them. The reason? I had specified that I would accept cash, but had not specified that buyers should not send cash through the post. What fucking idiots send cash through the post? Apart from it being absolutely bleeding obvious, it is also completely within eBay's power to warn buyers not to post cash themselves, they could put a big warning in bold red type right next to the option. I have now relisted my item with the following warning:

Please note: ebay cancelled my previous auction because I did not specify that cash should not be sent by post, so please remember not to send cash by post. Also, do not play with sharp knives, use matches/lighters near petrol, or jump off cliffs.