It seems like ecotourism is always the answer whenever a third world country's interest in improving their economy runs into everyone's interest in conservation.

I wonder, though, how big the market for these destinations is, and how many such places it can support. Even assuming that everyone who traveled abroad was a firm believer in low-impact environmentally-friendly hospitality, how many people could afford to travel internationally and stay in the middle of nowhere (which eliminates business travelers, who have to be in or near cities or industrial areas)? How long before these places are simply poaching each others' customers?

Your question is valid indeed. Eco-Tourism is but a modern marketing theme attempting to cash in on the glassy eyed arm-chair pundents who rarely have ever done more than lie on a beach getting sunburned or a good sun stroke or both. Today it is important for everyone to get out into the ECO System and preview this wonderful world. The difficulty with this is once the footprint of human excitement takes hold the ECO System is forever changed. As a practitioner in the Tourism Industry there is the signs going overboard in ECO Tourism will modify all parts of the natural state of our world. Taking great care to simplify this impact is a part of GEO Tourism which many marketers have no clue. They just jump on the flavour of the day and push it until a new flavour is introduced. The true ECO Traveler has ALWAYS been sensitive to the earth. The new ECO Traveler travels as yet with oversized boots and loud noises.