Normally when you cast a spell that affects a target at range there are clues as to where you are (streaking ball of fire shooting across the room, hands glowing like the sun, that sort of thing). I'd like stealthy options for magic where the target just catches fire and doesn't know who did it. I wonder if Skyrim will be capable of that.
The target would be aware that someone is there (well, unless they believe in spontaneous orc combustion) but would have to look for you, giving you a chance to get a spell or two more off first or even stay hidden if they can't find you.