I use Ebay a lot (feedback score 199) I have sold a handful of things but mainly buy and sometimes snipe (using Justsnipe to bid in last few seconds)
I bought a paper shredder early last year and on opening the box there was no shredder, just 4 wrapped christmas presents. I wrote to the seller to say 'so you thought you got a shredder from your mum and dad - you didnt' - I got a refund and they got their xmas presents in February
