The other day I discovered a body on the way to Bruma - an NPC, not a bandit. I didn't kill him and I wasn't around when he died so I can only assume it was a wolf or something and he couldn't defend himself. He only had a dagger on him and it wasn't equipped. Poor bloke. I'd never met him before, but I'd be devastated if it was an NPC I actually liked.
I love it when this happens. There's just this dead body, nobody around, no creature that could have killed it. This is one of the best features of Oblivion imo...this sort of randomness!
Yes, Bethesda solved this "problem" by simply preventing you from killing quest NPCs.
And yes, I think it's a somewhat strange and lame approach. But it's hard to see what alternative was available. They could do something like have an indication that the NPC is quest related (maybe a scroll over icon). But the problem with that is that some NPCs might be killed by other NPCs or Creatures, robbing you of that quest.
They coulda maybe had some essential NPCs act like chickens. Like if there's any sort of combat, they go off and hide somewhere. :bolt: But I understand this would take a lot of programming which Bethesda probably couldn't accomplish at the time for a variety of reasons. I'm also hearing Skyrim is gonna have some sort of ways around essential NPCs which isn't as basic (lame) as Oblivion's, but I forget how it's supposed to work. I know with some NPCs, like if it's a shopkeeper that gets killed, a family member of him or her can possibly take over the shop.