it's not just the dead themselves. People have friends and family. How would a widow feel, for instance, if she knew parts of her dead husband's body had been taken for reuse? She might think that's fine. But equally, she might find the thought upsetting and disturbing. If her husband had expressly agreed that this should happen, I think she would just have to live with it. But if it was done merely because he'd never got around to opting out - well, I think that's wrong. In the 19th century graverobbers used to dig up the bodies of the recently dead and sell them to surgeons to practise on. I can see the advantages of being operated on by a surgeon who'd had a bit of practice; but I still think that's wrong too.