Masks are an abiding human fascination, offering the possibility of transformation, anonymity, aggression, or protection. Or, in the case of the current swine flu outbreak, something more akin to pseudo-protection. The government-issued surgical masks in Mexico City make going out in public without as much fear possible, but perhaps at the cost of easier communication. I once asked a surgeon friend of mine whether he thought communication might work better in the OR if the medical team wore transparent surgical masks. He said he didn't think so—though I couldn't see his face at the time, so who knows?
I can tell you from my experience in Beijing that having an entire city of masked people is devastating to the social fabric. It is hard to have conversation through a mask—you can’t see smiles or frowns. Also, not all masks are equal. A good mask, well fitted and worn properly, is uncomfortable and hard to breathe through. And wearing a mask casually draped over your ears is more of a totem against disease than a scientifically valid form of protection.