Is Athenahealth CEO Jonathan Bush in a bubble?

Johnathan Bush, the Athenahealth CEO, believes his company can become the Amazon of health care. But hedge fund manager David Einhorn and others are betting that his soaring stock is ready to burst. Bush's gonzo approach to corporate leadership has worked spectacularly well at Athenahealth so far. Since the company went public in 2007, its shares had returned 266% through mid-December, more than double the Nasdaq (87%) or the Russell 1000 Health Care Index (130%) over the same period.