seems to me, that donating parts of youself, is not only conscienscious, but is more ecologically sound...
first of all, there's that embalming fluid, which can delay decomposition for years, and might contaminate soil and water... the less of you buried, the better. Then there's cremation, which produces an oily black smoke, which is obviously bad for the air... the less there is to cremate, the less pollution would be produced. There may even be an energy issue, here... does it cost less to crematea few pounds of tissue, than an entire body? common sense would say yes, but then, again, wouldn't cost the same to heat an entire cremation chamber regardless of what's in it? Hmmm.
and, if face transplants become common, eventually, substitutes will be made for donated skin... already, they are working with plastics that can integrate with living tissue, and hold such tissue in place until it grows in. They're even working with plastic matrices that will slowly dissolve, allowing the grafted skin to gradually take over for it. It may indeed, become possible to order a new face, without resorting to cadavers. a combination of plastic surgery and artificialy grown tissue grafts could be used to give you just about any 'look' you want... it might even be possible one day to reassign ethnicity. Talk about your scary thoughts... we're getting into Twilight Zone territory, here. And it isn't a matter of 'if', but 'when', and the 'when' is bearing down on us...
What will this mean? Ultimately, laws will have to be put in place, similar to laws to limit name changes today. These laws will, if enforced properly, keep felons from from changing their appearance to elude the law. But, of course, once the technology is perfected, there will be places and doctors who will do the work for the apprpriate fees. Imagine the business such doctors could do in dictatorships. Dictators already employ doubles, but imagine their being able to create duplicates, right down to the fingerprints (Cause, you know, fingerprints will be the next thing to be reassigned and/or repaired...).
In conjunction with computer Generated graphics, which are advancing with each new CGI movie, we will one day need forenzic teams, to tell truth from lies, and one person for another...
on a more fascitious note: Do you suppose that this is why the grey aliens all look alike? They are so advanced, they've taken this technology to it's ultimate extreme?