I'd have to say I agree with blueheaven and 
Evilminion. The claims would have to have some 
sort of substantial evidence to back it up (legal 
documentation would be nice). Otherwise, just 
saying, "Hey man, that's stolen!" is heresay and 
not gonna cut it. 

And knowing *before* you purchase anything is 
different than finding out something you bought 
sometime ago was swiped somewhere along the 
lines. 

If I knew without a doubt that a cel was stolen 
and was being sold under false pretenses, even if 
it's a dreamcel, I wouldn't buy it. Because if I 
knew, then other people would as well, which 
means I couldn't show it off or share it with 
anyone. Then it would kind of be like the Tell-
tale Heart, you know?

If I found out later that a cel in my collection 
had originally been stolen from someone 
(regardless of who they are; private collector or 
studio) - honestly, I don't know what I'd do. I 
wouldn't even know where to begin to retrace the 
steps of where and when I bought it, nor how to 
find out if the original owner wanted it back or 
whatnot. *shrugs*

Back to having solid proof, if legal actions were 
taken, then... couldn't we be at least bullied 
with charges of "receiving stolen goods". That's 
a small-time crime in the USA, isn't it?

But that's all pretty much beside the point. To 
answer your question: IF I knew, I would not buy. 
But HOW would I know for certain? That's a 
whole 'nother chapter in the story to consider.