You can purchase an infinite number of pictures of, say, the Eiffel tower, and therefore there is no reason to either pay a lot of money for one, or to hire a photographer to take yet another. In fact, CD's full of them are on sale, royalty-free, for only a few dollars a disk. The prime value of an image now lies in its exclusivity. It's estimated that 80 percent of all image uses do not require any exclusivity, and therefore 80 percent of the market is more or less economically uninteresting. At least that last 20 percent should be immune from any further changes in technology, because exclusivity will always be valuable.
Photojournalism is somewhat analogous.
Feature work is somewhat the same, largely due to the ocean of good feature work out there, except for when exclusivity comes into play and the subject is desirable. Celebrity paparazzi shots are good examples of extremely valuable commodities, but again only as long as the competing tabloid can't get its hands on them. Probably the most enduring and profitable market for images will be marketed through vehicles like Vanity Fair. They need marquee names for their covers and they've got the budgets to make almost any shoot a marketable event. Annie Leibovitz can marshal hundreds of thousands of dollars to get famous people into huge sets and create images that impress by sheer bombast.