“I don’t know what they all mean, but we do try to keep them from getting too weird,” he says. Levchin runs ads on his applications, but his thinking doesn’t stop there. “Our Top Friends app lets you buy drinks for your friends,” he explains. “So I think, What brand can be sponsoring one of our drinks?” He expects to make a million dollars by the end of the year on ad revenue alone. “Any big brands that want to simply drive traffic to their own Web sites are going to miss the chance to leverage the viral tools Facebook offers,” he says.

Fast Company