This has been an interesting thread and I would like to add a few observations.
I know of two photographers who sell prints on the web and seem to make money doing so. Dave Beckerman in NYC http://www.davebeckerman.com/
and Mike Johnson http://theonlinephotographer.blogspot.com/ .
Beckerman sells B&W inkjets from 35mm film and Johnson inkjets from digital. Johnson puts up some type of print each week for either $55 or $95 and if my memory is correct has sold about 10 of the $95 prints each week since he started a few weeks ago.
Beckerman's images are mostly street shots and architecture of NYC, very good but nothing spectacular. Johnson's are usually interesting, but nothing exceptional.
They sell prints becuase they have cultivated a presence through their web sites and specifically their blogs that generate interest. Johnson in some ways also has an advantatge similar to Brooks Jensen in that he is well known to most folks who have been in photography for a long time as an editior of various photo mags and currently writing for Black and White Photography. So he has an audience that due to sheer numbers will generate some kind of print sales. Interstingly enough, I don't believe Johnson, Beckerman or Jensen have any kind of gallery representation. In Johnsons's case, his website does not promote his photography but is more like an online Pop Photography magazine. Selling the prints seemed to pop up as a nice alternative revenue stream.
As with many things, the examples above point out that sometimes salesmanship or the online personae can be just as important as the images themselves.
Like someone pointed out above, it takes years to be successful. Johnson and and Jensen have been involved in writing about photography for close to 30 years each and Beckerman while having a website/blog since only 1999 has been photographing for 30+ years.