"Everyone loves shocking Apple news, and today, we have it -- admittedly, not in the sense you might be thinking. You know those white earbuds everyone and their mother wears these days? The ones that let you rock out with your... uh, iPod out? Apple now says they could shock you. Literally."
I guess there was enough complaining that they actually had to issue a support article on this at Apple. I've had other earbuds shock me, mostly when I've been in dry, low humidity environments, which seems to be the case here. Static electricity can build up for a variety of reasons and give you a mild shock. I guess when its in your ear it sure seems more than mild thus the support article. So if you are concerned, they have several suggestions such as wearing more natural fibers or my personal favorite of spraying anti-static spray in the air prior to using your ipod. I'm sure your fellow commuters will love that one. You could also avoid wearing your earbuds if you are in an environment prone to static electricity, or at least touch some ungrounded metal before putting them in your ears, but that would be too easy I guess.
Oh, and never ever use the top step on your ladder, especially when wearing earbuds that shock you!