I love the absolute glory of commerce, and the survival of the fittest, that is eBay.
Hundreds of thousands - maybe even millions - of things for sale. Sellers' skills in describing their offerings, the competitiveness of their pricing, and their ability to "think like a customer" (use relevant keywords, offer good pictures & detailed descriptions, etc.) all determine whether they'll be successful or not.
Buyers have to actually pay for what they bought before it gets shipped out to them. And if they're especially stupid, and don't read the whole description, they can buy something that wasn't what they thought it was... and too bad for them, nobody's going to wipe the tears from their eyes and protect them from the consequences of their laziness. You didn't read the description, and you didn't realize you were bidding on a PICTURE of a plasma TV, not the TV itself? Sorry. Item was exactly the way it was described - you bought it. Did you really think you were gonna get something worth $3,000 for $3.00?
Consequences for everyone are nearly instant. Did you bid, but not pay? Bad feedback for you, buyer, and no product either. Did you lie about what you were selling? Bad feedback and maybe have the money returned to the buyer (depending on how they paid). Make no effort as a buyer? Some other bidder will "snipe" your bargain - stealing it away with a pennies higher bid at the last second. Make no effort as a seller? No one bids.
Bid wisely, pay promptly, and buy from sellers with positive (more than 96 rating) feedback - and you can find bargains galore; delights not commonly seen in your local mega-mall. As a seller, list a full description, provide plenty of photos, ship promptly, and you can clear out your clutter while making some cash.
The system isn't perfect. But by golly, it's good.