The online music-streaming field is littered with the corpses of failed services. As companies like Spiral Frog and Napster found out, it is hard to make an honest living giving away music for free. In 2008, Pandora was on the verge of collapse, but while other start-ups have come and gone, Pandora has rebounded. In 2009, the company cleared $50 million in revenue; this year that number could be around $100 million. The New York Times has an article on the subject here.