You can't help being among the world's wealthiest folk if, like Paul Gardner Allen (1953-), if you happen to co-found Microsoft.

Allen's worth is estimated at $16 billion.

Born in Seattle, Allen befriended Bill Gates while in school. Both shared an enthusiasm for computers, and would regularly sneak into University of Washington labs to work on projects. They were eventually caught, but managed an agreement with administrators by providing free computer help to students who needed it.

Allen attended Washington State University, dropping out two years later to write software. He also convinced Gates to drop out of Harvard, to found the company that would make them famous.

A few years ago, Allen was back in the news for funding the SpaceShipOne sub-orbital commercial spacecraft. As always, the sky continues to be the limit.

Image: SpaceShipOne designer Burt Rutan (R) and project donor Paul Allen pose in front of the craft at the Smithsonian National Air and Space Museum in Washington, DC. | Photograph: Karen Bleier/AFP/Getty Images