I'm friends with a guy who was 'bought out' of his startup for north of $8M and he said something I found interesting.

"Chuck its not about the money, until there is a lot of money and you're not getting it. I mean when its all hypothetical you can be generous, but when its not hypothetical, and the piece being offered is not what you had informally agreed upon, you tend to stop seeing what you're getting and instead focus on what you are not getting. That can be toxic."

I think its just basic human nature.