Ken Haas draws attention to problems with getting refunds from developers and the Apple Store. I've had a bad experience like many others with inadvertent in-app purchases made by my kids through stuff like TapZoo, etc and run up $200+ charges. Apple and the developers were kind enough to reverse the charges, but after that, I have explicitly disabled in-app purchases, which should be the default.
Apart from the difficulty in getting refunds, Apple's model of storing your iTunes password for 15 minutes after its entered and indiscriminately passing authentication information between apps for in-app purchases is the nub of the inadvertent in-app purchase problem.
In typical Apple fashion, though these problems have been known and reported for years, its unlikely they will be fixed.