I've always felt kind of torn on the subject. But honestly, I don't like pranks. In general I think they're unkind, especially when done to a child, an animal, an elderly person, or someone already stressed/distraught or not in good mental health.
I've always really hated two things: 1) seeing people embarrased. god, do I hate that. And 2) (even more so) seeing people become dissapointed. It tears me up to see someone become happy just to be dissapointed when they discover they are having some joke played on them.
But, that's just me.
So what does everyone else think...?