Yes, that about sums it up but your post has made me think about this a bit more. Having no experience of selling on ebay I learnt a bit about it from reading what you wrote and as a result have changed what I think a bit. I still find it rude to ask a seller without a BIN what their BIN is but I can see the point in asking a seller if he would care to add a BIN. As you point out, it might be welcomed. That and making an offer seem fine.

Another thing, I see now that my original post had 2 points and yes, as you said, I did say I thought it was sleazy to try and get an advantage by asking what a sellers BIN was. I subsequently made a hash of explaining myself. I don't think it is sleazy to engage a seller and suggest adding a BIN or making an offer to end the auction but I do think putting a seller on the spot by asking what their BIN is when one isn't included is rude and a bit of a sleazy way to go about things.

Thanks for taking the time to lay out your thoughts.