My AP is in my wallet when I go, along with my credit cards. Never had them demagnetized by the x-ray scanner. I did hear that the x-ray machines used to scan checked luggage are set higher than the ones at security, USAirways advises not to pack film in checked luggage.
Regarding magnets, I have a friend whose AP was constantly demagnetizing. They kept asking her if she kept it near credit cards and she said no. After going through about 5 passes, they realized the problem was the magnet clasp on her purse, her AP passed over it when she put it back in her purse.