Mark Cuban is the owner of the Dallas Mavericks basketball team, as well as Magnolia Pictures and the Landmark Theaters chain. As if that weren't enough to keep him busy, he also serves as chairman of HDNet, a television station that broadcasts exclusively in high-definition. As of March 2011, his estimated net worth is $2.5 billion .
In 1999, Cuban bought a Gulfstream V, a private plane normally used for business travel that's sometimes used as a military vehicle. It set him back $40 million, and it also earned him a spot in the Guinness Book of Records , as it constituted the single most expensive e-commerce transaction in history.