Great topic and answers. I’d agree that these shoes allow more proprioception but are not much more apt to protect a foot from falling weights as a regular shoe. I have seen many a gym goer lose a toenail or two after dropping 5 or 10lb weights on their sneakers. The main thing I have seen people do to hurt themselves in a Vibram type shoe is snagging their pinky toe on random equipment, walls or even when their foot rotates on rubber flooring and the shoes “stick.”
Some of the most common “foot-related” injuries that occur in a gym setting (and here I’m using the generic term GYM, meaning not just weightlifting) are (in no particular order), impact injuries like dropping weights on the foot, twisted ankles and slip and falls. The toe shoes that I’m familiar with may offer some help with slipping since they have rubber soles. While not offering a lot of top foot protection, I tend to agree that they may be no worse then regular tennis or even fitness shoes. But lastly, they don’t seem to offer much (if any) ankle or lateral support if they’re being used in more movement based activities (I’d hate to think of someone using them on a basketball court for example – which some gyms have).
So, I guess that my answer would be “it depends…” Sorry.