Hijacked Accounts
My account was similarly hijacked earlier this year. I e-mailed spoof @ebay.co.uk straight away and they sorted it in hours. What the hijacker can do, having short-auctioned an expensive item, is get the money and run. The winning buyer then expects the true owner to either supply the kit or give a refund.
The only think I can thing of that compromised my details was my use of Auctionsniper.com (bids for an item as close as you want to the end of auction when you're not around to do it). I'd used it before successfully but, on this occasion, it needed my eBay password (as it would, to bid). Anyway, Mr Dummy's not doing that again.
GBZ