Bleeding-edge entrepreneurRank: 43Why he matters: After selling the PayPal online payment system to eBay for $1.5 billion, Musk has parlayed his estimated $334 million in personal wealth into three revolutionary ventures: electric cars, solar panels, and low-cost space travel.
As chairman and chief checkwriter at Tesla Motors (see No. 19), he hopes to give the electric car market a big jolt. Musk's SpaceX has successfully launched its Falcon rocket, a bargain at $7 million per flight, with hopes of muscling its way into the multibillion-dollar satellite launch business. Then there's Solar City, another Musk company, which encourages neighborhoods to share the cost of installing solar panels.
We assume Musk has his eye on a synergy play: humans driving solar-charged Teslas on the moon!
Meet 50 Who Matter winner Gina Bianchini. Her site, Ning, lets anyone be a social networking mogul. (more) 
