ClickZ reports that Arbitron will jump back into online radio ratings, having formed a new partnership with comScore to help collect data. Previously, Arbitron had developed its own network of client-side user monitors that measured streaming audio use, but the research company said it proved too costly to continue to roll out. According to Arbitron, media buyers have renewed interest in online radio because of the lack of ad clutter and desire to reach people at work. An Arbitron VP of marketing said the product will be pushed to traditional media buyers, not online shops.