As I was reading through this thread, I was 
mentally composing my own answer... but it seems 
that Jennifer beat me to it.  *grin*

Yes, I adore the thrill of victory when an auction 
ends and a cel is mine, or when I get a note from 
a dealer saying that the newly updated treasures I 
requested are still available.  But that thrill is 
the realization that another piece of fantastic 
animation art is now mine to adore and enjoy.

There's nothing I hate worse than discovering that 
I'm bidding against somebody that I know, and I've 
often ignored an auction simply because I 
recognize the bidding name of an acquaintance.  
I've also stepped back from quite a few sales and 
auctions in favor of a friend who tells me that 
it's something they want... unless, of course, I'm 
planning to get it for them either as a present or 
as trade fodder.  ;)  And I know they've done the 
same for me.

Competition, for me, would cheapen the intrinsic 
value of what I collect... if I ever discover that 
the reason I've just purchased or bid on something 
is because I want to beat somebody else to it, or 
because I want people to feel jealous of me for 
having it, that's the day I take my gallery 
offline and reevaluate why I'm collecting.

Of course, with that said, I would be lying if I 
didn't admit to a rush of sheer joy when I outbid 
a dealer on YJ the other day... *grin*  But that's 
primarily because if I hadn't, I'd have been 
paying a LOT more for the cel when it came up on 
his site later... aaaaiiieeeeeee!!