I have had nothing but good experiences using 'Facebook'. Allthe people that I knew that use it have also had good experiences writing and finding people they have lost contact with over the years.
The site has its pros and cons. If you're smart about what you do on here and listen to the numerous warnings against posting private information to an entire network of strangers, your safety won't be compromised. Some third-party applications are a bit questionable, but that's at your discretion. Don't click on links prompting you to "check out this funny video of me LOL" or anything of the like. It's most likely spam. Good antivirus and antimalware software will hopefully prevent anything terribly dangerous from sneaking on your system.