I didn't say Facebook is a selling site....both Facebook and auction sites are full of strangers that we probably have nowt in common with and wouldn't meet up with them in the real world.
People post all sorts of dodgy things on these forums and then the posts get picked up by google for anyone to read...so there isn't a great deal of difference in the safety rules we need to be aware of.
I have to say though...nobody on here has thrown a snowball at me recently, nor sent me a well worn teddy bear (maybe Meebo might send me one)