Just to second the point that return policies boost sales, I will buy from Amazon over other distributors, even though I usually shift the format to epub and read on a different device. The return policy is one of the reasons.
In contract, I despise the Android market, which has a 15 minute return policy.
I've probably returned two books since 2007, both accidents of hitting the buy button when I didn't mean to.
I've surely returned 10 Android market apps because the 15 minute review didn't convince me it did what it said.