Age: 38 and 36
Rank change: Up
With Twitter firmly entrenched in the cultural zeitgeist, its congenial odd-couple founders -- Williams is the cerebral one, Stone the jokester -- have been redesigning the site, pushing hard for revenue in the form of "sponsored tweet" ads, and beefing up management: Witness last month's promotion of COO Dick Costolo to CEO. (Williams will step aside to focus on product strategy.) Could Twitter finally be growing up?
Friendly competition: Williams has 1.3 million followers; Stone has 1.6 million. (Says Williams: "He's more famous, but I'm better at tweeting.")
NEXT: 4. Raul Vazquez
Last updated October 14 2010: 1:25 PM ET