How Facebook can destroy you
Employment: Want a job? Have a job you want to keep? Delete your drunk-at-a-party photos and shave off the "#%@$ my job" statuses, because it's likely that your employer (or potential employer) is going to run an internet search on you. And unless you have fortress-like privacy settings (discussed below), they're going to get a glimpse into your personal life. If you're seen as a partier, or somebody who disses their current/old jobs or managers, or generally shows low class, you could easily lose your job.
Identity theft: Have your address, phone number, or birthday ANYWHERE on Facebook? Be prepared to have credit cards made under your name by strangers and used feverishly without you realizing. ID thieves have absolute field days when people post private information publicly. And if you think only your friends will see your number or BBM pin in those groups, "Need your numbers," you're wrong. Almost all of them are open to friends of friends, entire networks, or all of Facebook—revealing your number to thousands, if not millions, of strangers.
Property crime: Going on vacation? Don't tell the world. A status detailing that your house will be empty for seven days exposes your property to all sorts of crime. Why take the risk?
How to stay safe
1. Use a strong password.
2. Hide your birthday.
3. Don't mention your kids.
4. Don't mention your vacations.
5. Don't let the young'uns try it out.
6. Keep photos to yourself.
7. Adjust your settings.