I hate all junk mail in my inbox, but chain letters are even worse, because they are sent by people who are supposed to be your friends, yet they waste your time with these stupid chain letters. It really frustrates me as well.
I neve get them anymore and here is my secret. Once I get an initial chain letter from somone. I send them a reply politely asking them not to waste my time with anymore stupid chain letters, because I don't find them entertaining, and I don't read them so even sending me one is wasting both our time. Then if they are my friend, they simply stop sending them to, and if they continue, then they are not my friend and I block them. easy as that
I still get the occasional one on accident, but they are few and far between.