Wow, you are a babe in the woods. This is the day of google stats and metrics, spiders, bots, trojan horses and the greatest gift to marketers and hackers everywhere.......METADATA!
Look at the URL of your FB page. There isn't even an 's' at the end of 'http'. Your information is passing back and forth without encryption.
Don't put any information on an insecure site that could be used by an identity crook.
When a person fills out one of those surveys it always asks permission to mine your data. How polite! Who writes those apps? Are they putting those on FB just for your entertainment. Read the license agreement that you agreed to when you joined.
I'm not saying Facebook isn't a great thing. I encourage my friends and family to join. But remember, you are giving information to somebody and you need to be vigilante in your caution regarding out that info may be used.
How does the guy in Nigeria have access to my PI if he isn't my friend? I don't accept friends that I don't know.