Enron rose to Fortune 500 stardom in the oil trading business, but by the time company entered its well-documented tailspin in the early part of this decade, it was mainly leveraged in a different commodity: High-grade Texas snake oil.

Director Alex Gibney doesn't exactly scoop the competition in “Enron: The Smartest Guys in the Room” — everything in this lucid, sardonic documentary is a matter of public record. Still, the film is invaluable, the clearest, most damning glimpse yet of a bona fide capitalist horror story.

There's less irony in the title than you might imagine. For all their arrogance, these guys really were smart: Enron chairman Ken Lay held a Ph.D. in economics; CEO Jeff Skilling was a Harvard MBA. And with their smarts came hubris: Enron stock would never fall on their watch.

Fostering a Nietzschean corporate culture designed to deify profits, Enron executives devised schemes to artificially inflate the company's value. They bullied analysts. They commissioned dummy companies to hide debt. They abused an accounting method known as “mark-to-market,” whereby hypothetical profits could be placed on the books and passed off as real income. When the pyramid collapsed, they cashed out, leaving their work force with near-worthless pension and retirement funds.

Gibney punctuates Enron's sins with a wry selection of pop songs (the best: Judy Garland singing “That Old Black Magic”) and uses his well-informed talking heads (including Bethany McLean and Peter Elkind, on whose best-selling exposé the movie is based) to maximum effect. Interestingly, many of them use Titanic-themed metaphors to describe Enron's downfall.

Free-market advocate Joseph Schumpeter once predicted that capitalism would eventually cannibalize itself, and the Enron episode is a troubling reminder of his words. At one point in the film, a pundit points out that the company, by squeezing the system, effectively undermined its own goal of deregulation. Which brings to mind one of Enron's favorite corporate catchphrases: Why?