To cut down on potential scam attempts and other problems, and to take the onus off members having to 'police' threads, how about a rule like this?
Sellers with less than 3 positive feedback ratings on HUKD must include the following on all FS/T listings: (1) A picture of the actual item/s for sale with their username next to it. (2) Confirmation of whether or not they will allow collection, and if so, from where. (3) Details of feedback held elsewhere, including username/s for possible verification. Members with 3+ positive feedback on HUKD are not required to post these details but are encouraged to do so where appropriate or when asked.
Just an idea - It's obviously not foolproof but it might add a bit more protection against 'hit and run' scammers. At the very least it gives other members something to point to - the scam attempts I have noticed on here have employed lots of different strategies to avoid answering these questions from members.