Closing The Box: A note from Pandora founder Tim Westergren details the company's plans to cap free mobile listening at 40 hours per month. Saying that "limiting listening is a very unusual thing to do, and very contrary to our mission," Westergren points to rising royalty rates and says the plan, which will affect only 4% of users "allows us to manage these escalating costs with minimal listener disruption." Read the entire letter here.