As a seller on eBay, what always gets me is that the market is driven by the sellers. That's a good channel of distribution for new products that consumers might not otherwise know about; On the other hand, there are also sellers trying to sell products that nobody wants, or products that have a very low demand. That's bad for both sellers AND buyers; sellers lose money, and buyers have to push through a ton of noise to find their signal.
What's the solution? A marketplace driven by buyers. This ensures that the amount of products never exceeds the consumer demand - less noise and a lot more signal (or perhaps ALL signal). It ensures that sellers find their target audience and don't waste money on distribution channels that won't work. Everyone gets what they want.