I disagree with the eyeglass mounting being dangerous. I used the Third Eye eyeglass mount until it broke recently. Most of the mirror clips over the side of the glasses (the arms?), and only the mirror protrudes in from of my left lens. Worst I could imagine would be a good scrape on the side of my skull from the broken plastic or the plastic mirror hitting my lenses. If you're wearing eye protection, a mirror shouldn't be any more of a risk than a junebug.
I have a Blackburn helmet mount now. I find this one harder to adjust properly, but it snaps off it's mount plate very easy, similar to the one Portis shows above. I bumped it on my locker and the thing popped off off immediately, so I feel the same way about the helmet mount as far as safety goes.