How the brief was written scared me a little, but 37Signals charges a pretty decent amount to post a listing so I figured it was all going to be kosher.
So, the question here is: why didn't you trust your gut feeling? Why did you value your (simplistic) rationalization more?
I can't speak for him but it's probably the part where the guy insisted on a payment method that he could back out of after receiving the final product and wouldn't accept two reasonable options that he was less likely to be able to back out of.
As I commented before I think it is a bit of me still trying to give everyone a chance. From the brief it did seem like that something was off. I just have to keep developing on letting certain "opportunities" pass at certain times.
So, the question here is: why didn't you trust your gut feeling? Why did you value your (simplistic) rationalization more?