Yes; a vendor I'd worked with asked about what 
other cels I might be interested in. I showed 
them my wishlist page, and it turned out they had 
access to a cel that was the exact same as a 
screencap I'd made.

I've never had a problem with people using my 
gallery to try and buy things from me, but the 
series I concentrate on are much less-sought-
after than those a lot of others collect. The 
only time I've had anyone query after one of my 
cels was after I participated in a show-me thread.