I've managed to anger the shopkeeper or his friends in many ways in Spelunky by blowing them up unintentionally or destroying their shop with a boulder. I've had shopkeepers show up in other levels if I managed to get away, and kill me there as well, so they don't seem to forget. The other shopkeepers also seem to know if you've killed another shopkeeper, and they go after you as well.
Is there any way to get a shopkeeper to forgive you after they call you a terrorist, or are you pretty much out of luck in using the shops after you've killed one?