But eBay is like a mall, complete with a specialty store catering to the most arcane collectors. Collectors are not known for their discipline or restraint. It's easy to wake up one day to discovery your previously healthy bank balance has been transformed into a mushrooming accumulation of alarm clocks, beer signs, or tiki mugs. There are bargains to be had on eBay. But it's also quite easy to get sucked into paying more than you wanted by the heat of the auction.
Bidding can get bloody.
The process is a little convoluted. As in a traditional auction, the computer always shows the amount of the current bid. Instead, you indicate the maximum bid you're willing to make. The winner is the person with the highest maximum bid. But this isn't necessarily what they have to pay.