I understand how all that works. I just haven't ever had any problem with people trying to get kicks that way. Usually the joker wants some form of reward for their efforts.
I can't imagine someone requesting the email and then jumping up-and-down with glee at the thought of an unrequested email going to the owner of the email address. In most cases they wouldn't even have any conformation that their joke worked unless their friend tells them.
If you have that kind of problem already, then it might be worth annoying all of your customers to prevent that kind of abuse. I haven't had a single complaint. I keep my registration forms to the bare minimum necessary to do business with the customers. People hate filling out forms.
When I find people messing with my server, I just ban their IP address from connecting to my server. It's pretty easy to tell who's up to no good by the area's they're trying to access.