I seldom buy a product that doesn't offer a blanket (if you aren't satisfied for any reason, you can return it) kind of guarantee. It's a risk reversal strategy and if you tell me I must implement a strategy that I haven't even seen yet, in order to test and see if it works, before I can get a refund, you aren't reversing my risk. I want the ability to return a product if I read it and it doesn't fit into my business model, or if it's just crap.
I understand that it's frustrating for the content provider when it seems like the end user didn't even give it a try, or if they are just asking for a refund and going to use it anyway, but I think the sales you lose with a 'strings attached' guarantee probably out weigh any of these problems.
I think this is one of those situations where you're stepping over dollars to pick up nickles.