Email|Link|Comments (1) Posted by David Beard, Boston.com Staff May 27, 2008 12:10 PM By Carolyn Y. Johnson, Globe Staff Amid concerns the planet is warming, the market for clean, green technology is beginning to show signs of overheating, too. more stories like this"I call it the global warming bubble," said Bob Metcalfe, who knows something about bubbles. An inventor of the ethernet and founder