The 2009 TIME 100 Finalists

AGE: 24
OCCUPATION: Facebook founder
PREVIOUS APPEARANCES ON THE TIME 100: 1

PRO: With Facebook's population inching toward 200 million — even your grandma's on it, though her status updates are usually pretty lame — Zuckerberg is managing the fastest-growing social-networking site on the Web.

CON: A recent dustup over the site's terms of service — many feared their tipsy Wall-to-Walls might become permanent Facebook property — demonstrated just how quickly users could turn against Zuckerberg's creation.