Apple was reported to have introduced new restrictions on App Store developers to prevent them from cutting it out of the value chain when using in-app purchasing, with Sony being the first high-profile casualty of the regime change. In Sony’s case, the issue is related to an e-book reader app, which allows customers to buy content from the Sony Reader Store without Apple receiving a share of the payment price. Now, all purchases have to use Apple as a middleman, enabling the company to get its 30 percent share of the proceeds.

Recent research from Distimo indicates that in-app purchases are becoming increasingly popular as a way of generating additional revenue from both paid-for and free apps. It now appears that the company is looking to ensure that it does not lose its share of this revenue, with the New York Times citing analyst comments that Apple has recognised that “the unit of economic value is the platform, not the device.”

While a number of apps across a range of product categories are moving toward in-app purchases, the issue is especially relevant when it comes to ebook apps and similar. Here, the value of the app is actually the content that it enables access to, rather than the handset software itself, making in-app purchases essential to the business model. With margins in many publishing businesses already tight and prices pressured, Apple’s decision to add itself as an intermediary in the value chain is only likely to create further friction. A number of high-profile publishers have either already launched or are planning premium products for the iPad.