Just months after introducing a 40 hour per month cap on free mobile listening for its online radio service, Pandora has announced that it will remove the limit starting September 1st. Pandora first added the limitation in March due to increased licensing costs, noting that just 4 percent of users would be affected by it. The company says it can now return to the unlimited option because of the “rapid progress of its mobile advertising”. Following the release of a disappointing guidance in its second quarter results on Thursday, investors pushed Pandora’s stock down more than 7 percent in after-hours trading.