Aidan- I have a Facebook account but strongly suggest you don't mix personal and coins. It wouldn't be hard to find out where you live through Facebook and take all your stuff.
I have a Facebook account also. I try to leave the real personal information out as well. Maybe I need to find out more about the numismatic groups on there.
I have a Facebook account as well. I have actually traded coins by meeting people on Coin Network, and then continuing friendships on Facebook. I know it's risky, but I have only traded a small amount at a time.