Seven years ago this month Houston energy company Enron collapsed and spurred financial regulations that were meant to prevent the kind of corporate mischief that led to that historic flame-out .

Well, these days it looks like those regs did little to protect the U.S. financial system from the latest round of shenanigans, and the ensuing meltdown that has cost investors billions and thrown the global economy into a tailspin.

What did we learn from Enron? It might be easier to see what we didn't:

1. Leverage, hidden or otherwise, can be lethal.

"The difference is that Enron went under when it was leveraged 11 to 1 whereas at Lehman it was more like 30 to 1," says John Olson, an energy hedge fund manager, who was a lonely critic in the 1990s of Enron's arcane accounting when he was a Merrill Lynch analyst. Enron bigs eventually had him fired from that job.

2. Top Executives Aren't Boy Scouts

Enron-inspired regulations in the 2002 Sarbanes-Oxley Act "were just for show" and "didn't do anything," says Dean Baker, co-director of the Center for Economic and Policy Research in Washington.  The legislation included provisions requiring executives to personally sign off on financial statements and increased the amount of outside capital that must be at risk in special purpose entities.

At the trial of Enron executives Jeffrey Skilling and Kenneth Lay, jurors dozed and looked at the ceiling during testimony about the company’s complicated and risky investments. They ended up convicting on the more straightforward charges that Skilling and Lay "presented a rosier picture of the company than they knew to be true," says Andrew Weissmann, the former director of the Department of Justice's Enron Task Force and now a partner at Jenner & Block in New York.  

And that may be how Wall Street executives will be held accountable. "There are definitely investigations now as to whether the heads of A.I.G. and Lehman did the same thing as things were going down," Mr. Weissmann says, referring to their repeated public statements that their companies were sound.