(L to R) Jack Dorsey and Biz Stone of Twitter.
AGE: 33 and 34, respectively
OCCUPATION: Twitter co-founders
PREVIOUS APPEARANCES ON THE TIME 100: 0
PRO: Their straightforward status-sharing program — user messages are limited to a mere 140 characters — has evolved from a charming distraction to a nimble, wide-ranging media platform, documenting major events (the attacks on Mumbai, the Flight 1549 landing) in real time.
CON: Although the site's population numbers 6 million (and growing), its revenue-making potential seems largely untapped.