"Why Telling People They Don’t Need Masks Backfired: To help manage the shortage, the authorities sent a message that made them untrustworthy."

https://www.nytimes.com/2020/03/17/opinion/coronavirus-face-...

And some data back from SARS: "Always wearing a mask when going out was associated with a 70% reduction in risk compared with never wearing a mask. Wearing a mask intermittently was associated with a smaller yet significant reduction in risk."

https://wwwnc.cdc.gov/eid/article/10/2/03-0730_article

I saw a lot of people sanctimoniously talking about fit tests in normal healthcare settings as if an imperfect fit dropped effectiveness immediately down to 0% from 100%.