(FORTUNE Magazine) - In what universe is it even conceivable that the United States could fail to reach the semifinals of something called the World Baseball Classic? Not only fail to win, but could field a team that included Roger Clemens, Derek Jeter, Alex Rodriguez, and Johnny Damon and then lose games to Mexico, South Korea, and - wait for it - Canada? Yet it happened this year.

How could a movie starring Brad Pitt, George Clooney, Catherine Zeta-Jones, and Julia Roberts, directed by Steven Soderbergh, get tepid reviews and gross less worldwide than the star-free My Big Fat Greek Wedding? That movie was Ocean's Twelve.

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Special Reportfull coverage Why dream teams fail Ten offbeat teams that work The team that saved Motorola Can Stringer recharge Sony?

Bad teams Lessons from the business playbook John Rigas, Timothy Rigas, Michael Rigas The paterfamilias, John, and his sons borrowed huge sums for personal use. Adelphia went into bankruptcy in 2002 after disclosing billions in debt. Much of the Rigas clan ended up in court. CEO Phil Condit (1996-2003) and his Boeing brain trust Dogged by scandal, falling earnings, and the challenge of Airbus, America's premier airplane manufacturer just couldn't fly right. Al Dunlap and anyone "Chainsaw Al" liked to portray himself as a tough-minded savior of dying companies (Lily-Tulip, Scott Paper, Sunbeam). But the big-talking bully got tossed from Sunbeam and ended up as a symbol of capitalism at its worst.

And how could a FORTUNE 500 company run by a brilliant former McKinsey consultant, paying fat salaries to graduates of America's elite business schools, dissolve into fraud and bankruptcy? It happened at Enron.

If someone tells you you're being recruited onto a dream team, maybe you should run. In our team-obsessed age, the concept of the dream team has become irresistible. But it's brutally clear that they often blow up. Why? Because they're not teams. They're just bunches of people.

A look at why so many dream teams fail, and why so many of the most successful teams consist of individuals you've never heard of, yields insight into the essential nature of winning organizations. As always when the subject is the real-world behavior of human beings, the takeaway includes things we always knew - even though we rarely behave as if we do.

The most important lesson about team performance is that the basic theory of the dream team is wrong. You cannot assemble a group of stars and then sit back to watch them conquer the world. You can't even count on them to avoid embarrassment. The 2004 U.S. Olympic basketball team consisted entirely of NBA stars; it finished third and lost to Lithuania.

By contrast, the 1980 hockey team that beat the Soviets at the Lake Placid Olympics was built explicitly on anti-dream-team principles. Coach Herb Brooks, who died in 2003, based his picks on personal chemistry. In the story's movie version, "Miracle," Brooks' assistant looks at the roster and objects that many of the country's greatest college players were left out (professionals were not eligible to play then). To which Brooks responds with this essential anti-dream-team philosophy: "I'm not lookin' for the best players, Craig. I'm lookin' for the right players."

To see why dream teams so often disappoint, let's consider the most common paths to failure.

• Signing too many all-stars
• Failing to build a culture of trust
• Tolerating competing agendas
• Letting conflicts fester
• Hiding from the real issues