If patients are dissatisfied with their care, it is difficult to dispute since they already have been charged for it, says Mark Rukavina, who heads the Access Project, a Boston-based health-care advocacy organization.

WSJ: Is Your Doctor Pushing Credit Cards?

Fabien Cousteau, founder of Plant a Fish, an educational and ocean-restoration project in New York, has used online platforms to process web-based donations for his organization, which doesn't have the staff to open envelopes, deposit checks and organize spreadsheets.

WSJ: Fee Bite for Web Donations