There were reports of traders being refused access to some US exchanges where, unlike the UK, dealers still trade on vast trading floors in brightly coloured jackets.

If a dealer ever traded with a thief, they would immediately be cut off from their source of supply.

The large spreads (up to 25%) and thin markets of many penny shares are reminiscent of the OTC market, and indeed most licensed dealers have traded in both.

EJV - short for Electronic Joint Venture - hoped to gain market share by offering lower costs of execution when primary dealers traded with each other.

'So you can use one dealer to trade with the rest and get control of a company?'

In advance of today's $12 billion auction of 30-year Treasury bonds, dealers were trading the issue with a yield of about 8.15 percent.

In advance of today's auction of $11 billion of new five-year Treasury notes, dealers traded the issue at about 5.18 percent, down from 5.19 percent.

And the upheaval in the secondary markets, where dealers, brokers and investors trade bonds after they are issued, is bound to prove more profound.

Today, there are basically two ways to trade stocks: through the continuous auction market on an exchange floor or over electronic screens, where dealers trade stocks directly among themselves based on Big Board prices.

This is where dealers trade directly with one another or through inter-dealer brokers (i.e. companies like GFI Group and BGC Partners.