Bill Joy's green investing ideas [video]

At a Churchill Club event in Santa Clara, Calif., Bill Joy, co-founder of Sun Microsystems and partner at Kleiner Perkins Caufield & Byers, explains how his company came up with 26 "grand challenge areas"--areas where the company, along with Al Gore and his staff, can make the biggest impact on the environment. Joy says for an idea to excite him, it has to be able to make a significant change in the world, but it also has to have been researched enough to prove it viable.