Techcrunch ran one of their big, blazing headlines today reporting "Apple’s iPhone App Refund Policies Could Bankrupt Developers". They cited Apple's contract which allows for Apple to charge developers 100% of a refund, even though devs only get 70% of the payment to begin with. Under that model, developers would get hit for 30% extra each time an App Store purchase was refunded. Not nice, for certain. But apparently also not (yet?) the case.
TiPb contacted several developers to find out what was going on. While some were aware of the potential for a 100% refund charge back, none had experienced it. Uniformly, they reported very few refunds, and when they did occur, charge backs only for the same 70% cut Apple had originally passed along to them.
For now, at least, Apple is eating whatever processing, administration, and other charges that occur out of their own, 30% cut.
In general, all the developers we spoke with hadn't seen many returns and didn't seem to consider this a huge problem right now. This might be because the process of getting a refund is not easy to begin with. If that changes, as recently discussed on Twitter, it could become a greater concern.
As to Techcrunch's other charge, that a refunded app becomes unusable, we've been unable to find an occurrence of that in the real world. If you've had a refund on any apps, let us know if it goes dead, keeps working but won't upgrade, or stays the same.