To those that say they don't understand why someone wouldn't donate either their own or their loved ones organs, go back and read Buscakes post and open your mind a little bit.
Understanding a bit more why someone doesn't want to donate would be nice, but it doesn't actually matter whether it's understood or not. It does need to be accepted, respected, and not judged negatively though.
It's lovely that in the worst of times people can get some comfort from doing something that carries out a wish of their loved one, or from knowing that their organs have helped someone else, but people are different, will experience grief very differently, and especially will react very differently in those fist hours after being told their loved one has died. That's just people, and choosing not to donate is perfectly valid. The fact that people get comfort from donating their loved ones organs proves that it isn't entirely altruistic, and while it's a wonderful thing when it does provide comfort, if it doesn't then it shouldn't happen.
In response to the point about how there's not much talk on the thread about the recipients of donated organs, with all respect, it's not about them until after a potential donor has died. I mean properly died, as in both body and brain. Until then, it has to be about the potential donor and their family and what's best for them. It would be horrific, and bordering on barbaric if families were to have no say at all in the decision.
Fwiw, as far as I can say without actually being in the situation, I'd be fine with not accepting an organ as I don't want to donate.