I actually think the CDC recommendation is misleading and possibly does more harm than good because many folks believe the cloth mask will protect them. And consider the logical flip side: if moisture can get in to infect you, it certainly can get out to infect others so it is not really protecting them either. The theory on masks is that they minimize the transmission and every little bit helps. But I think the CDC would be better off saying they have minimal impact and should stress that touching, washing and keeping distance has a much more significant value in reducing spread.
initially, there was not a recommendation to wear masks for this exact reason. the message was that masks that provide true protection need to be directed to health care workers. they acknowledged other masks were of limited help in protecting one's self from the virus -- particularly when most people don't know how to properly wear them. (case in point: just today i saw a guy in the store with an N95 mask on... but he had it pulled down so his nose was exposed.)
that was updated because, while masks are of limited use, their impact is not zero. the lack of direction on masks prompted criticism since, given the gravity of the current situation, every effort to protect ones self is helpful. that said, every medical professional i've seen commenting on this has emphasized the need to use masks
as well as other precautions such as hand washing, not touching one's face and social distancing.
so while i'm unsure of how much my mask is protecting me or others, i find there are several very practical reasons to continue using them.
first; it makes me far more conscious of my behavior. without a mask i'm very likely to touch my face without thinking. with it, i tend to think about it when the urge to do so occurs. second, it's a signal to others that i am taking precautions. i find folks are more likely to give you extra space when you have them on. lastly, there is an aspect of social acceptance. the more folks that wear them, the less stigma there is for folks that absolutely have to wear them in public.
and to tie this topic back into our running interests, there have been concerns about people outside exercising without masks in places that have been particularly hard hit. this story gives a good summary with links to other articles that have been written about it (but be ready for quite a few curse words):
https://slate.com/technology/2020/04/runners-masks-coronavirus.html
bottom line: most experts say the criticism is unfounded and the risk runners without masks pose to others is minimal if nonexistent. personally, i will wear a mask when i will be in close contact with other people (like when grocery shopping) but not when running where i can put a significant distance between myself and anyone else (i try to keep at least 10 feet from other folks). in both cases i try to go out stupid early when the number of folks i will encounter is minimal.
EDIT: there/their