Hello,
Sorry not to be able to find the link again, I think it was on drudgereport.com. anyway the guy was showing that facebook logs everything you type even if you don't send the message. so I believe that if you ever logged your device to facebook, it's unsafe to be used with btc. Wrong?
Everyone should know that facebook basically owns the data you put on it. It's not a place for privacy, your posting for the world.
That being said storing anything secret or important in a facebook message would be a horrible idea. You could post you public bitcoin address. But private key, and such should never meet facebook.