Related: Meet the small businesses making millions from online marketplaces Becky Campbell, managing director of Kent-based digital marketing agency Reflect Digital, agrees: "More competition just proves your market".
New digital companies such as Uber and the accommodations website Airbnb are at the forefront of the "sharing economy", which challenges traditional business models by encouraging peer-to-peer marketplaces.
A wave of consolidation among hospitals has strengthened their position in the local marketplaces within which they operate.
It would be better for the SEC to scrap rules forcing different marketplaces to share their quotes, and let traders choose for themselves to direct their business to whichever they think is the most efficient.
For those not convinced that it does, a new breed of private exchange is gaining popularity where shares are not sold in public offerings but instead are placed with large investors, who are free to trade them later in the secondary market.Banks and exchange operators alike are taking an interest in creating such hybrid marketplaces.
Yet others, such as News Corporation and Time Warner, are staying vertically integrated for now, and trying to combine old-media empires with new-media marketplaces (MySpace and AOL, respectively).
Their vast computerised hubs and their ability to zip transactions around the world in split-seconds allow them to play a dual role reminiscent of the marketplaces and sailing ships of medieval times.
Ventro's marketplaces have been shut down, three-quarters of its staff have been sacked and its shares are now trading below $1 (see chart).
There is a madcap drive from the airstrip to the city: those who reach the market first receive the best price.Mogadishu's marketplaces, Bakara and Hamarweyne, bustle with enterprise.
As it is written, the law authorises the Internal Revenue Service to offer tax credits to Americans who buy health insurance on "exchanges", or online marketplaces, "established by the state".
They have not only continuously expanded their offerings, but are curating their mobile marketplaces to fit a smartphone screen.
