Character Karma

One of the well-known clichés of horror movies is having an opening scene in which the teenagers who break the rules--drinking, doing drugs, having sex, etc.--are the first victims of the monster/serial killer/psycho.  And in action movies, children and dogs never die.

In writing, how important is it that the character "deserve" an unhappy ending? Alternatively, do the bad guys need to be punished in order for the reader to have closure?

Consider It's a Wonderful Life. Should Mr. Potter have had something bad happen to him? Did it bother you that he got away with it?

What do you think?