I agree with Jason and Chris; simply refuse to enter exhibitions with ridiculous fees, and explain why if asked. Petitions and web-forum ramparts sound nice but are often an empty exercise in misplaced idealism.

Eddy, I can see your point; no one thinks putting on an exhibit is or should be free. Whether it makes sense for you to put on an exhibit and charge fees is a market-based business decision, just as it is for an individual photographer to decide whether to pay those fees against an uncertain chance of ROI. I'm pretty sure that for many photographers, high gallery commissions and heavy exhibition entry fees are no longer part of a viable business model for selling one's work.

This is the beauty of the marketplace: if exhibitions with high fees are good venues for moving one's work, word'll get around and demand for those display slots, and prices event organizers can charge, will reflect that market-based decision. If not, well....time for everyone--including the organizers--to rethink what makes sense.