Yeah that's true. However I noticed yesterday, when I hung my Ear buds on my Cube wall at work. "BING" the suddenly moved over 3 inches to the metal strips on the edge of the walls. I'm curious as to how strong a Magnetic field they actually have. I have several other pairs of earphones and none have actually stuck to my cube wall before. I'm kind of worried about the strong magnetic fields flowing to each other using my brain as a conduit.
Magnetic fields themselves are harmless from what I understand, and are even used for healing by some beliefs.
Electromagnetic fields are a bit different and are heavily suspected in cancer cases and birth defects. The main difference is the mount of power passing through with the electricity, increasing the field.
But to get down to it, your headphones are not going to cause brain damage or cancer, or all the people that bought walkmans all those years ago would be battling or have battled cancer right now, as shielding technology was not what it is now. So you have nothing to worry about.
But then again, I'm neither a scientist or a medical doctor, so I could be just blowing sunshine up your butt.
I do have to tell you, this past summer I went to visit my wife's family in Kentucky. The hills were they live have the huge powerlines running overhead. You can go to the top of the hill and sit down with old radio. Even without batteries it plays great. Kind of makes you wonder if they shielded those old powerlines at all.