I don't know why you are not getting replies on this. We cant be the only two. I have the same problem and it is a critical problem for a company phone. I only stream on Wi-Fi and this random playback is causing me 3G data expense problems with my employer. I made sure that I had pressed "stop" and closed last.fm. Still, when I got in my car, I found my phone was streaming the last tag I had played in last.fm and I didn't even know it had been doing it for a while, because I didn't have the BT audio channel active. We should be able to set limits so that particular apps can only use wi-fi, and can only run in the foreground with permission. This has happened several times, and all I can say is, you have to be on your guard, or uninstall your music players. I will have to remove all such apps before I take my next trip to Europe to avoid a massive roaming penalty. If your music player allows you to pin stations to the start menu. don't do that either! Now just periodically look at my sign on screen to see if it's got a player on it . I have pinned the "stop music app" to my start screen and I run it several times after I stop playing music. Things seem a little better now but I do not trust last.fm nor WP to do the right thing. The way WP handles music players is incompetent.