Donated blood in the US is rigorously tested. Even if you don't pay people, it's entirely possible that someone doesn't realize that they have HIV or some othe

Donated blood in the US is rigorously tested. Even if you don't pay people, it's entirely possible that someone doesn't realize that they have HIV or some other disease. CDC page on blood testing: https://www.cdc.gov/bloodsafety/basics.html https://www.cdc.gov/bloodsafety/basics.html