The French found with the Maginot Line in the late 1930s that building a barrier does not keep people out. The East Germans found out 30 years later that it doesn't necessarily keep people in. And after more than a decade of building walls around the US capital markets, the Securities and Exchange Commission appears to be learning the lessons from both.

Christopher Cox, chairman of the SEC, likes the Maginot Line as a parable for securities regulators. He said: "In a world where capital and information can quickly race around any regulatory Maginot Line or just scurry over it, we'd be well advised to constantly reconsider our regulatory defences in light of the changing conditions."