How bad is the earbud?

MP3, MP4, iPod and the like has replaced the old Sony Walkman that I grew up with. With these new innovations come the earbud headphones as opposed to the old over-the-ear kind.

My father never bought me a Walkman arguing it can damaged hearing. Is this true? Whether old or new, headphones have the capacity to damage hearing if we used it at high volume for a long time.

A Harvard study found out that adults who listened to music with their headphones for more than an hour  and a half at 80% volume experienced permanent hearing loss.

So a little discipline wouldn't hurt. Perhaps this is what my father has been trying to tell me?!