There's also the memory of meeting the person who 
did the signing. Something that a buyer of an 
autographed cel won't have. When I had my Tasuki 
cel signed by Watase Yuu, I also have fond 
memories of what she said about my cel (I could 
tell she wanted it. She just kinda sat there 
staring at it longingly before signing it). ^_^;;

A signed cel not only comes with a signature, but 
precious memories.

I also agree about the aesthetic look of an 
autograph on a cel. I've seen cels with a dark 
background bearing a signature in black (or a cel 
that's mostly dark being signed in dark colored 
marker). What's the use of getting a cel signed 
if you can't see the signature? Hoi...

~Nabs-chan