So your definitive source is some blogger who runs a website called "surfing the net with kids"?
How about the FIRST link in your google search, a time magazine article where they interviewed an audiologist who says
"I don't want to single out iPods. Any personal listening device out there has the potential to be used in a way that will cause hearing loss. We've conducted studies of a few MP3 players and found very similar results across the MP3 manufacturers. Some in-the-ear earphones are capable of providing higher sound levels than some over-the-ear earphones. That said, studies we've done on behavior show that the type of earphones has almost nothing to do with the level at which people set their headphones. It's all dictated by the level of background noise in their listening environment. When we put people in different listening environments, like flying in an airplane — we used noise we'd recorded while flying on a Boeing 757 commercial flight, and we simulated that environment in our lab — 80% of people listened at levels that would eventually put their hearing at risk. On the subway system here in Boston, the ambient noise levels are very comparable to the level on an airplane, although it sounds very different. The noise is sufficiently high that it induces people to listen to their headphones at excessively loud volume."
In that regard, in ears are SAFER because they isolate the outside sound an allow you to use a lower volume level. As the expert says:
" I would also strongly recommend that people invest in better earphones that block out background noise."
Its about the listening volume and duration, not the style of the headphone or even the proximity to the ear drum.