The market isn't being "eroded" by people giving away their work. The market was "eroded" by the fact that there are literally hundreds, possibly thousands, of people in the U.S. alone who are now skilled enough to regularly take what were once considered "professional" level photographs. There is simply too much supply.
If you want to blame someone, blame Canon and Nikon and Olympus and Sigma. Blame capitalism for giving us such unprecedented wealth that huge swaths of the population now have free time to study, scout, take, edit, and publish photos. Don't blame the artists.