I remember a short story - title and author escape me - where this was actually much like what was going on. Everyone had their relevant types on file, and if some number of people needed an organ you could supply, you were harvested for said organs. The protagonist got notified that there were nearly enough people who needed his organs and he went undercover and visited them all, thinking he'd kill one and get out of it, but he finds that they aren't what he expected (e.g. the one who needs a liver is a girl with hepatitis, not some drunk) and decides not to, and then one dies anyway and he's off the hook.