I think dibs should be honored because as far as 
I'm concerned it is a promise -- I don't really 
trust people who knowingly go back on their word. 
I'd much rather people be honest. If it's a 
friend then I will be more understanding if he or 
she needs the money more than I can pay. There 
are also other instances where one might not 
remember who the cel was promised to...that can 
be problematic (thus "dibs" should be kept 
informally among good friends I think). 

But if it's just a matter of money and the person 
either blows me off or lies to me about the 
situation, then I write off that person forever 
as someone I want to sell to/buy from.

Wendy