I like ebay,
if only because on occasion I can find cels from people
who dont have websites. I also like the way feedback 
works, and the added security it gives (of course its not 
perfect, as some people dont care about feedback etc).

I like to sell there because I get a buyer quicker than if
I were to attempt to sell on my website. There are also
anime cel collectors who arent well acquainted with this 
site (cels.org / animanga forum) whom I've managed to
 sell to from ebay, and so I guess it does get you
 through to a wider market. I've also met some great sellers
there whose websites I would never have found otherwise!

Sure it sucks when something I want goes for more money
than I would pay. It sucks worse when I pay more than I 
rationally would ^^ But thats how auctions work, and 
being an occasional seller I greatly appreciate what Ebay
has done for my finances.