"The term covers (and promises) a lot, and a quick Google search fills in quite a bit of the territory. One enthusiast snagged the domain name, but there are plenty of others in the game.
One site notes that vernacular photography is '...one of the most affordable areas of collecting and therefore offers wonderful opportunities for the beginner to acquire beautiful examples of photographic art at very reasonable prices.' gargantuaphotos.com poses the basic question: 'Why would I buy someone else's crappy old photos?', and thefoundphoto.com is another gallery/vendor.
Boston University hosted Vernacular Reframed, 'a two-day interdisciplinary conference examining issues in vernacular photography' in November 2004, but lots of enthusiasts are in the game as well: Square America, bighappyfunhouse.com, and Junior Bonner blogs about the phenomenon. Some specialize in specific genres, like photobooth and African American Vernacular Photography. Ookpik specializes in Michigan photographs, happy palace has an eclectic (and ever-growing) mix, greywater posts 'photographs from films I processed that I found in old cameras...', and eBay has a Vernacular Photography Enthusiasts group with more than 100 members.
Serious scholarship is not far behind: Electronic Journal of Vernacular Photography may be stillborn, but Innocence regained? Or just another kind of fiction? from eye magazine suggests that there are many who take the medium seriously. One is Geoffrey Batchen who taught a course at CUNY's Graduate Center (there's a video of a lecture he gave at Brown)
Quite a few museums have had vernacular photography shows, including Kodak and the Rise of Amateur Photography at New York's Metropolitan Museum, and this grant proposal from the Indiana University Archives Seeing the Color of America: Digitizing the Charles Cushman Collection is evidence of archival interest in the medium.
My friend Joan Larcom reminds me of one of the authorities who has done the most in this realm, Michael Lesy, and his coinage of the term demotic photography, which I find a good supplement to 'vernacular'. A New York Times story notes that:
'In the past, Mr. Lesy has ruffled some academic feathers by arguing that what he calls 'demotic photography,' like family snapshots or picture postcards, deserves the same level of scholarly study traditionally given only to art photography... 'my whole intention is to subvert the [art photography] canon... There are possibilities that go beyond the safe definitions of what an artist is and what the camera is used for. ...Academics... deal with photographs as aesthetic, intellectual constructs, or as integers in philosophical or linguistic argument. That's not all they are. They're slippery and deeply emotionally charged. A photograph is a thing which, to use an old scholarly word, needs to be 'unpacked.' There's the manifest content, then half a dozen layered contents.'
(NYT 17 Dec 2005 sec B pg 9)"
(Hugh Blackmer, oook.info)