This should probably be in the selling areas, but there are so many stickies in there it is hard to see anything, and I think it is quite important, although hard to stop.
There are a current number of "Man in the middle" scams being tried, both here and on other forums.
How this scam works is that someone is selling something on the forum like this:
GoodSeller: I am selling this expensive bass, I am not shipping it
GoodBuyer: Oh thats just what I want, will you ship it
GoodSeller: No, I said I wouldn't!
then someone looks at that interaction, and creates an account GoodSel1er, where there is a 1 instead of an L, a complelete different username, but looks really similar, then he sends a message to the buyer:
GoodSel1er -> GoodBuyer: Hey I have changed my mind, do you want to me to ship it? I can send it to you by paypal F&F for £20.
GoodBuyer-> GoodSel1er: Great thanks, you have lots of good feedback I will buy it off you. <sends money>
then a week later, angry buyer posts on sellers real post 'you are a scammer you haven't sent me anything', and of course it is the first that the real seller has heard of it. BadSeller has trousered the money and is off with it, and because it is either a bank transfer or a f&f, you have no comeback.
Obviously the answer is not to accept F&F or bank transfer, and ask for additional photos etc as usual, but additionally, be really sure who you are talking to - if someone messages you offering you something that is on the forum, go to that post, click on their username and select 'send message' to reply, then you know you are talking to the right person.