Here's why you shouldn't wear your iPod during a thunderstorm:
Doctors at Vancouver General Hospital in Canada said a 37-year-old jogger wearing an iPod was burned on his chest, neck and face after the man and a nearby tree were struck by lightning in 2005. The burns traced the path of the earphones, they said. [...]
The metal in the earphones helped channel the current and cause the injuries, they said.
"Although the use of a device such as an iPod may not increase the chances of being struck by lightning, in this case, the combination of sweat and metal earphones directed the current to, and through, the patient's head," they said.
Update 7/15/07: New image by Dumidu - Thanks!