The more urgent it sounds, the more skeptical you should be. Even if you think it might be true, let someone else spread it. Imagine you received a package in your real homes mailbox asking you to place your house keys in the return envelope provided, and mail them to a post office box. People fall for the computer version of this all the time. It is very very easy to frame someone with an e-mail message or Usenet post.
All someone has to do is sit at their computer when the victim is away from the keyboard.
But hackers can be much more sophisticated. They can forge any message to make it appear from anyone. Chain e-mail and Pyramid posts on Usenet are a scam, and most often, they are a crime. If you forward one, you will be blasted with hundreds of angry messages in reply. Many hoaxes encourage their victims to forward a message to as many people as possible in order to get a reward for themselves or on the behalf of some charity.