Facebook is huge with soon 500 million users worldwide. And bad people try to abuse that large user base with different techniques and methods. One that I came across today is a scam email which wants to you view some photos. If you click the link, Facebook asks you for your password and to verify that you want to add a new email address to your profile. Do not do this!
You may wonder why people want to add an email address to your profile. The reason is, that if you do this, they can request a password reset and can then use your Facebook profile.