"People always told me photos have been done," says Kevin Systrom, cofounder of Instagram. "My feeling was, These people are wrong." To wit: In just nine months, his photosharing platform—which enables anyone with an iPhone to snap pics, apply one-click filters, and instantly post the results—has amassed more than 3 million users, who upload some 20,000 images an hour, a figure that balloons on weekends and holidays. Rather than merely archive pictures, "we think about photos like, This is your tweet, this is your status update," says Systrom, whose personal Instagram uploads include a brownie bin marked "munchies" ("You know you're at the Haight Ashbury Whole Foods when ..."). His red-hot network is already luring brands such as CNN and Starbucks to post behind-thescenes pics. But Systrom is focused on scale. "Not 3 million users," he clarifies, "300 million."