Harvey's answer is way better.
Harvery said
"Actually, refrigerator magnets aren't magnets, at all. They're cold seeking osculators. When they sense cold on the other side of the refrigerator door, they suck real hard to try to get through it. Good thing refrigerator doors are made of steel. "
its more accurate, I would go with this one to maxamize marks.
The reason only one side sticks, is because the cold seeking osculators are located in a vary narrow band of the "fridge magnet". ie. in a few microns width in the center of the magnet. the side that sticks to the fridge is sand blasted smooth, so it sticks will to the fridge, this is why the sometimes dont stick to low quality fridges that have rough surfaces, because there is not enough surface contact.
the other side doesnt stick, because it is made to be rough... so that the plastic epoxy has something to stick to. otherwise the plastic would be too easy to peel off.
imagine a lawn, where the dirt are the cold seeking osculators, and the grass is the rough(hidden) side of the "fridge magnets" than if you look closely on a microscopic level, there is a large amount of seperation between the cold seeking osculators and there potential target. and unfortunately, it would be too expensive to make cold seeking osculators more powerfull.
that is the full answer to your problem.
in fact, you could just copy and paste it in to ms word, fix up the punctuation and change a couple words and hand it in!