I have sold one thing on eBay - an old sewing machine that went quickly, the lady came and picked it up and gave me the €20 in cash, job done.
On cleaning out a kitchen cupboard the other day, I decided to jettison an electric grater I had which I rarely use. Photo taken, ad uploaded, and almost immediately I got a reaction. Rather odd wording, but I replied, saying, no, it hadn't been sold yet. The chap then replied, asking for my e mail address. I didn't see the point of this, as all communication,could easily be carried out on the eBay site through the messenger system.
But I thought it couldn't do any harm, and went to put it in the box and send the reply. A message popped up from eBay saying "It looks like you're sending sensitive information here - are you sure you want to do this?". So I didn't send it and rang my son who has more experience with eBay and IT security generally. He suggested just writing back and saying I'd rather keep it on the site (and not correspond privately via e mail) to be able to better keep track.
I did this and got as a reply a garbled message that looked as though it was copied from the eBay T&C, but which, on closer examination, didn't make any sense. Something about eBay requiring him to have the e mail address so they could send the confirmation of receipt and transfer the money.
I was really suspicious now due to (a) the formatting of the messages (not even a "hi" or any form of signoff (b) the wording of the messages (c) the fact that he was using "Sie" rather than "Du" which is more usual in this situation (d) on reflection, the speed he reacted to my advert was not natural and (s) the chap's name being the typical kind that foreigners invent to sound German, although it could also be bona fide.
Anyway, shortly after this exchange, I received an email from eBay saying to be beware of this user because the account was being used by scammers.
I'm glad I trusted my instincts and am quite proud of myself for recognising this as a dubious customer.
What would be clear signs of a scam to you and do you have any examples - e.g. where the language has been so ridiculous that it was obviously not genuine?