I never have yet which surprises me greatly, 
particularly when I sniper several similar items 
(not just cels) on eBay. The way I look at it is 
I go to work all week and I should spend my money 
as I please and plus, if I want to get up at five 
o'clock in the morning to place a last minute bid 
then that's my perogative. 
Sometimes I've done that and still been outbid. 
I've learnt now just to shrug and walk away; 
obviously the other person put more value on the 
item than I did.
Personally I think the internet gives people the 
confidence to be far more bolshy than they would 
be in real life. I get a bit pissed off when I 
get emails telling me what I should put on my 
website (none cel related). Frankly, I don't mind 
sharing my doujinshi collection with others but I 
don't appreciate demanding emails telling me to 
scan more of my doujins because they want to see 
them but don't want to buy them. I wouldn't dream 
of mailing someone to be rude or pushy but 
obviously not everyone thinks like that...