Here are 2 items I found by doing a Google. It used to be said "do not take part in ANY chain letter." Now here is some advice from 2 sources. In all my 75 years I have never seen a chain that was not unbroken. No one ever got what they hoped to get. The P.O. made money off the postage and the sender gave up something, but often wound up with nothing. I don't think times have changed that much.
http://www.cs.rutgers.edu/~watrous/chain-letters.html
http://www.howtoadvice.com/ChainLetters
June