I personally like the idea of allowing others to make use of these useful organs, especially since the original owner can't use them anymore and they'll decay within days (if not hours).

That said I don't agree with forcing people to something they don't want to and I know that there are at least a couple of religions out there that forbid cutting up the body after death.

The 'forced choice' option (in one of the other comments) is a really good one, IMHO