Businesses are paying Twitter $120,000 to sponsor a promoted trending topic for a day, director of revenue Adam Bain told marketing news site ClickZ. That's up from $25,000 to $30,000 when the feature was launched in April 2010. Bain also said Twitter is expanding its sales force to 60 people and pursuing smaller brands by offering promoted accounts and promoted tweets in an auction-pricing system. Twitter has worked with 600 advertisers on 6,000 campaigns since it launched ads last April, Bain said.