The only thing that's bad for the typical user of the iPhone/iPod is playing their crappy music too loud and too long...and that's not an iPhone/iPod thing, that's a dumb human thing. Ears were not made for prolonged high-decibal noise pumped directly into the canal.
I had to put up with someone's thrash metal on the train home last night (which made it a looong 45min)...I could hear every cymbal crash and shriek from 20-30 feet away. And the guy was in his 40s--so we can't always blame it on poor ignorant kids.
All things in moderation...the Greek's 'middle road' still makes the best general rule. Super-size-me Bigger-is-better Buy-more-save-more Americans, unfortunately, seem to have abandoned that a long time ago...myself included (can't claim total innocence here).