You shouldn't forward chain letters even if they're true. You definitely shouldn't forward them if they're false.
And the latest false warning doing the rounds is a perennial hoax - the so-called Invitation FACEBOOK/Olympic Torch virus warning.
Facebook users have been spreading a chain letter recommending that their friends post a notice to their walls prohibiting Facebook and the US government from using their content. It is a chain letter/hoax and has no legal merits.