Much has been written about Apple’s subscription and in-app purchasing policies. Basically, Apple requires that apps that sell content provide in-app purchasing through the iTunes App Store, which provides Apple with 30% of the sale. Apparently Google has a similar policy regarding in-app purchases, requiring that such purchases are done with Google Checkout, and they also take 30% of sales.
The Visual VoiceMail app was recently pulled from the Android Market because it did not use Google Checkout. Visual VoiceMail sells premium options like voicemail transcription through in-app purchases. The developer accepts payments via their web site, with a redirect to the web site from within the app. It should be noted that the Kindle app sells e-Books in a similar manner, so as is the case Apple, it will be interesting to see whether the big apps like the Kindle and Nook apps get pulled from the store.