Revenue generated this way is not necessarily new charity revenue. Some people will donate about the same amount of money to charities every year—what may vary is which ones get their attention.
I think you had the same misunderstanding as this person: http://lesswrong.com/lw/1qf/the_craigslist_revolution_a_realworld_application/1lth In short the idea is not to give free ads for charities, but to put up normal commercial advertisements and give the proceeds to charity.
Revenue generated this way is not necessarily new charity revenue. Some people will donate about the same amount of money to charities every year—what may vary is which ones get their attention.
I think you had the same misunderstanding as this person: http://lesswrong.com/lw/1qf/the_craigslist_revolution_a_realworld_application/1lth In short the idea is not to give free ads for charities, but to put up normal commercial advertisements and give the proceeds to charity.