In Battery Saver app for WP 8.1, there is an option to choose an app, whether it should run in the background or not. But from the last few days, I'm noticing MSN apps to behave in a different manner. On my Lumia I preferred MSN Weather, MSN News apps not to run in background, and set to Not Allowed from Battery Saver app. But next time when I open these apps and check these apps in Battery Saver it's again allowed to run in the background. So, I think Microsoft is forcefully trying its MSN Apps to run in background.