Kevin Systrom

Instagrammers, rejoice! You were indeed on to something when you came in droves to the new photo app two years ago. So were we: Systrom, No. 39 on last year’s list, this year sold his baby to Facebook for $1 billion (because $1 million isn’t cool). Systrom says the 16-person Instagram team is still independent within Facebook, and in 2013 will expand. Indeed, Systrom isn’t going anywhere: “Other people sell and check out,” he says, “but we have no interest in doing that. When the founders leave, that’s when the soul of a company goes away.” Mobilize: Word has it that Systrom will be a key player in beefing up Facebook’s mobile presence. –D.R.