[jen_h]

The other thing is that you're dependent on the validation server's availability to check the receipts. Apple's got great uptime in this respect (and others), but there have been outages (a big one last September: http://www.ilounge.com/index.php/news/comments/app-store-suf...).

It's a tradeoff, really, that most IAP implementors consider:

Cost of support and loss of goodwill when legitimate customers run into issues vs. loss of revenue from pirates (heretofore only jailbroken phone users) who likely wouldn't have purchased anyway.

It makes fiscal sense for big players with big IAP scale like Zynga to strictly validate. Little players may find it is less critical to the bottom line to be strict about it.

[flatline3]

You're also dependent on Apple's purchasing servers to buy the content to begin with, so I'm not sure I see the point.