Jimmy Wales wrote:
At the present time, no ISBN links on the wikipedia are generating any income for the Wikipedia. Perhaps in the future that should change, but we have to be very careful about such things, and in my experience, the amount of money from such links is so low that it isn't really that important... not important enough to damage our independent reputation.
Mindful of all the hazards of such things, this is certainly one of the less obtrusive financial aids that might be available should the situation ever call for it. Eclecticology