They have the advantage of being closer to true markets, such as stock exchanges, and thus better at lowering prices and improving liquidity by matching buyers and sellers.

ECONOMIST: Seller beware

The primary responsibility of a market maker is to maintain an orderly market by matching buyers and sellers of a security and to stand ready to buy or sell for their own account when there is a price imbalance.

FORBES: When Does Market Making Become Market Manipulation?

When it comes to business models, eBay's is an elegantly simple one: it takes a commission for matching buyers with sellers, leaving most of the tedious work, such as arranging payment and delivery, for the two parties to sort out. eBay is already profitable.

ECONOMIST: The future of e-tailing | The