IF INVESTING IN so-called clean technology ever had a Pied Piper, it would have to have been Vinod Khosla, the man who helped start Sun Microsystems and later founded an eponymous venture-capital company. From its inception in 2004, his Menlo Park, Calif.-based firm drew attention with outsize investments in companies such as Amyris (petroleum alternatives), Gevo (biofuels) and Kior (renewable fuels). Then, at a TechCrunch technology conference in September 2011, Khosla boasted of earning $1 billion in profits in one year