Now that I have embraced my facebook account I have to start telling everyone the same things that I talk about at work. Don't click on strangers. If someone sends an email to you and you don't know them, delete it.
"Cybercrime is rapidly spreading on Facebook as fraudsters prey on users who think the world's top social networking site is a safe haven on the Internet."
One of the ways they do this is guess simple passwords.
"Scammers break into accounts posing as friends of users, sending spam that directs them to websites that steal personal information and spread viruses. Hackers tend to take control of infected PCs for identity theft, spamming and other mischief."
I have dealt with spam, spyware, and viruses on more computers than I care to think about, so dont think this can't happen to you.