Having a large base of clients willing to buy through their services is ultimately what matters, and I think they achieved that partially by siding with the customer most of the time. Making a purchase through their services, you know that you more or less protected, and if you start jumping up and down, you will probably get your money back. Businesses put up with their less-than-fair treatment because until recently, there weren't any alternatives on nearly the same level of "respectability", as far as buyers are concerned.

I'm willing to bet that in the beginning, when they were mainly trying to court businesses to implement their service, the situation was different.