"Dropbox’s ascent has been just as stunning. The 50-million-user figure is up threefold from a year ago, and it has solved the “freemium” riddle, with revenue on track to hit $240 million in 2011 despite the fact that 96% of those users pay nothing. With only 70 staffers, mostly engineers, Dropbox grosses nearly three times more per employee than even the darling of business models, Google. Houston claims it’s already profitable but won’t reveal margins."
I should likely disclose that I LOVE Dropbox as a product, just love it.