I've only had this happen a few times, but it does worry me. I'll be walking down the street and notice that my pocket feels a bit warm. I check the iphone and it's running warm and the battery is mostly drained. I'm worried about both symptoms, as I don't want the thing to get damaged and I don't want it to run out of juice just when I need it most. All extra stuff is turned off when this happens (3g, bluetooth, wifi, etc.) except for location services. Does location services take up that much in the way of resources?