Heh. We always kind of snickered at folks wearing masks here before. It's such a good idea. It was never about preventing a disease, but, about preventing spread. If you were sick, you whacked on a mask so you didn't give your bugs to other folks.
And, largely, it works. I mean, you've got subways here, jammed to the rafters, day after day, and we're still not anywhere near an emergency. Say what you like, it does work.
On a side note, I took my daughter to the doctor today for a cold (just a cold thankfully), and, between waiting maybe 30 seconds to see the doctor, and the entire thing costing me 20 bucks between the consult and the perscription meds, I have to admit, Japan's really got it's health care system locked down.