Bettman/Corbis

[RAP]

The stock houses have certainly comodified the sale of photography and just about every other two dimensional media, paintings, graphics, etc. You can lisence AA images on Corbis. Muench also has images with them as well. You can buy fine art prints from famous artists who are long gone at huge discounts.

There are 10's of millions of images stored in these houses, maybe 100's of thousands of artists. There are also smaller agencies that sell and market images of the larger ones. This all leads to smaller commissions for the photographer/artist.

They can certainly control trends in what gets marketed to the masses, as to what the masses see and influence their thinking, public perception, and most important, how they spend their money. I am sure they also have a powerful influence on the spread of digital.

[SLNestler]

Anybody have any experience dealing with stock houses as a photographer? I heard one story where some contracts allow for images to be cut up and sold in pieces, altered in Photo Shop, and the photographer gets nothing for those usages.

There are still a few reputable houses, not owned by Getty or Gates, etc.
The market changes constantly. If you are seriously interested in dealing with a stock agency, it is worthwhile to join an organization like ASMP, where they constantly monitor these things, and can advise you on getting a good contract.
Steven