I do it all the time. ^_^;;  And I plan to go 
right on doing it, too.
I buy a lot of my cels for the character; it's my 
primary reason.  But both scene and art are also 
very important motivators for me.  And so while I 
may know nothing about the character, or even the 
scene, if I like the art enough I find I'll go 
for it.
More often than not, if I want a cel I know 
nothing about, I'll sit and wait a while on it..  
If somebody was a desperate, rabid fan, they'd 
have their chance.  But I really can't work 
myself up to feel the least bit guilty over 
buying a cel I know nothing about if it's been 
sitting on a site for sale for a week or so..  
Perhaps there's a rabid fan who didn't see it and 
would've wanted it..  But I can't say as there's 
anything stopping anyone from -asking- me about 
any of those cels.  I don't buy anything to make 
a profit, and I don't buy any cel with the intent 
of reselling, but I believe I make it clear that 
I'm always willing to listen, and I'm not one to 
get offended by inquiries, and so in that way I 
feel that I'm being fair about it..  
Beyond that, a number of cels I bought, knowing 
virtually nothing about the character, motivated 
me to look into a series/character, and get into 
the anime. (*cough*Guitar*cough*Sarutobi*hack*)

Eek.  Library closing.  Sorry for the disjointed 
post, I hope it wasn't too...rambly.  But it's 
hurried. ^_^;;

~Mala