My friend Dahni-El just emailed me this story from the BBC
Computing magazine Which? recovered 22,000 "deleted" files from eight computers purchased on eBay. Criminals source old computers from internet auction sites or in rubbish tips, to find users' valuable details. Freely available software can be used to recover files that users think they have permanently deleted.

The only solution, according to Which?, is complete destruction - and it recommends using a hammer.

I don't know about a hammer, but how about a baseball bat, a high kick and some Geto Boys? Pretty hot. I can now enact this scene in the name of computer security