It's the sustained use of high volume levels that is so dangerous. However I see that if someone uses a crappy headphone, they are more likely to drive it to excessively loud volumes in attempt to hear the more subtle parts of the music that the phones seem unable to deliver.
With very good headphones, the details are there and so someone is likely to drive it a bit lower volumes. Less damage to hearing accumulated over time.
With that, earbuds are intrinsically crappy - it's very hard to engineer good sounding ones, especially at a price point below $300. Since the craptacular buds provided with the iPod and it's ilk are so bad (seriously pure trash) I can see why so many think 128 kbps MP3 is fine - if everything sounds equally crappy, why bother to encode at a decent bit rate? I see people with those little horrors listening at volume levels so high I can hear the lyrics at two meters distance on a noisy city bus. Additionally in my case, ear buds are so ill fitting (can't stand them).
I far prefer big honkin' muff type phones, the kind with a coiled cord, decent drivers, and good isolation. When I see those used on the city bus, almost never do I hear music even at close range - only when the user pulls off the phones while still playing.
I prefer earbuds, with hearing protection ear muffs over them, with absolutely no background noise (its scary at first), you here things perfectly at a very low volume.