First, thanks for the answers so far. However, I guess I used the wrong word. I'm not concerned about making a living. When I said "viable" I meant from a "getting published" standpoint, as well from a "getting lots of readers" standpoint.
My concern is if readers are buying fewer short story books/magazines/website/e-zines/whatever and thus more venues are dying out than ever. If they're dying out, then there's fewer places to get published, a much stiffer competition because all the writers are submitting to the few remaining venues, and fewer readers reading those stories overall.
I see a hell of a lot of tiny publishers calling for the "40% of royalties split among all authors" anthologies and I know that not only will that never pay, it will also not sell. I see almost as many token pay open calls. While I don't want to submit somewhere that pays $.02/word or less, the money is secondary. What I'm worried about is 1) getting published in the first place 2) in somewhere that will reach as many readers as possible. I don't want to get a story in an anthology that won't sell, because then I just sold the first print rights to something no one will read because no one is buying; I'm out of decent pay AND a good story.
I also worry that short stories are not a way to recognition any longer. A lot of writers up to 20-30 years ago cut their teeth and gained notoriety with their short stories - primarily horror writers, but some Sci Fi writers too. Now I can't think of any authors in the last two decades who got big with their short stories. I say this because short stories are what I'm good at, novels are a beast I can't seem to tackle, so I'm worried there just aren't the readers there to build up a fanbase with.