You wouldn’t have to contribute to any one. If you desire the retailer could send the rebate to you through the site. Every sale made, a piece would go to the originating site. For example if you link to the site from Free Republic or a favorite charity and make a purchase, they would automatically get a contribution. The site would then contribute to one our favorite charities. All of this being paid for by the participating retailer.
Buy something you would normally buy, get money back and help a charity or your favorite blog. A win, win, win scenario.
Aha, the Amazon.com model. Now I understand.
There is a site, Deals of America, that directs viewers to retailers selling good deals. The site gets a cut of the profit for directing shoppers to the deals.
http://www.dealsofamerica.com/
Perhaps this model can help.