There are a multitude of scams around the Internet and even the most intelligent newcomers often get "taken in". Unfortunately, their naivety leads to the spread of these scams to other people, a few of whom will be gullible and "spread the word".
If you receive any message which invites you to "forward this" or "send this to all your friends" or "send a message to email@example.com" or similar, please DON'T (as web manager I often get various emailings like this. They take time to read, then, if they seem genuine, check up on. This all takes time that could be spent doing other, more productive, things).
The intention of these types of scams isn't always clear.
If an email address is given (send a message to firstname.lastname@example.org), then it's probable that the originator wants to fill up the owner's "in box" with useless information.
If there's a web site address then a "denial of service" attack is probably going to be the outcome (flooding the server until it is shut down/blocked).
Sometimes they are sent out just for the heck of it to see how many gullible people will believe them. In this case they may ask every, say, 100th person to send an email back to them so they can see how quickly it's spreading.
Even if it comes from someone you know and is passed on in good faith it may only mean that they have been taken in as well! (An easy way to spot this is you may notice that the same email has been sent to a lot of people (To: name1,name2,name3, etc. or the email starts: From: Person To: Someone......... From: Someone To: Someone........etc.) this type is often sent as a virus warning or other dire consiquence warning but I often get jokes, a welcome diversion, forwarded this way).
Whatever the reason they are sent, it's usually intended to cause a problem for somebody. If nothing else, it's going to swamp the Internet with a LOT of unnecessary messages. Some companies are considering a charge for every email routed through them because of things like this. By sending on these messages, you help to bring that day closer.