As Charlie Sheen Tweets, Twitter's Valuation Grows - NYTimes.com

As Charlie Sheen Tweets, Twitter's Valuation Grows - NYTimes.com: "For Mr. Sheen, Twitter has become a highly profitable endeavor. Through Ad.ly, a marketing service that matches celebrities and brands, Mr. Sheen is selling endorsements through Twitter messages — his current going rate, according to the report, is more than $50,000 per tweet."