Good stuff OnD
I've been using rare earth magnets for the past few years on my cars. I simply stick the magnet on the bottom of the filter and have yet to lose one. But I never had the desire or curiosity to open one up to see what was trapped. The magnets are replaced after three years of driving in the winter salt after the nickel plating disappears (though the magnet still works).
Lee Valley Tools (leevalley.com) also does mail order and stocks a wide variety of rare earth magnets and washers to help increase their power if you're having trouble finding them.
