Advice from GP's I work with is that they don't really help as they only protect for a brief time. Once they are damp, even from your own breath, they no longer work. So pointless all these people wearing the same mask all day.
Best to leave supplies for health professionals who really need them i think.
I was in the Accidents and Emergency department of a local hospital, about 3 weeks ago, and there was an oriental couple there, both with masks on. My opinion is that the wearers are to be applauded, because they obviously wish to be seen to be 'doing their bit' and are being as careful as they can.
Idiots mostly as they are wearing the wrong sort unless they are protecting others, stops their droplets coming out, will not stop the virus getting in only a respirator type level 45 I think will do that.