Followers: 391K
Sample tweet: "Amazing, in Libya, that everything is held hostage by the ego of one man, and the fortune he plundered while we winked."
When a battle with thyroid cancer rendered him unable to speak, film critic Roger Ebert turned to the Internet, transforming his blog and Twitter account into something much more than a narcissistic Web presence. He turned those tools into a voice. Now whenever the first film critic to win a Pulitzer "speaks," he does it directly to nearly 400,000 people — an audience that helped make him the Webby Awards' 2010 Person of the Year. And yes, he does tweet about film, but it's his scrutiny of the larger news cycle of the day that shouldn't be missed.