I've had a contact (about an tandem in the For Sale section) from a supposed buyer, who I'll not name as he would only change his name next time anyway. After exchanging a couple of emails I was almost at the point of providing contact details, address etc, when something he said made me suspicious - basically he lives abroad (allegedly) and would be happy to send someone else to collect the bike from me. This is a well-known scam. The gist of it is that the supposed buyer makes the payment via Paypal or Western Union or similar, gets someone else to collect the goods, and then raises a 'Damaged or Not as expected' dispute via Paypal. They then claim the money back from your account, but by that time the goods are gone. 
I have halted the deal now, but if anyone else sees a similar transaction brewing, the general advice is to please be very, very cautious and only proceed if you are absolutely certain it's genuine.