Maybe this sounds a bit silly but here goes:
I have Skype on my iPad3, and numerous times I will hear a phone call coming in that is SPAM over Skype. This of course happens when I'm way at the other end of the house and have to run run run to catch the call, only to find frustration.
Question: Is Skype running in the background even though I've never turned it on since the previous power-down? Related... I've noticed when I do that selective shut-down of apps (multi-finger up-swipe) that many apps are listed as running that I've never used.