Investors are falling over themselves to finance start-ups in clean technology, especially in energy. Venture Business Research reckons that investment in the field by venture capitalists and private-equity firms has quadrupled in the past two years, from some $500m in 2004 to almost $2 billion so far this year. The share of venture capital going into clean energy is rising rapidly (see chart 1). New Energy Finance, another research firm, reckons that investment of all sorts in the business will reach $63 billion this year, compared with just $30 billion in 2004. The lure of big money is leading investment banks to ramp up their analysis of the latest boom industry.