Apple takes a 30% cut of all in-app purchases including music streaming subscriptions, digital goods, and more. For some industries, 30% is a big portion of their profit margins. As $9.99 is the industry standard for streaming music services, it's possible that if rivals charged a higher subscription price (to offset Apple's cut), they'd lose customers to Apple Music.
One solution to avoid the 30% cut, is to have customers signup for subscriptions outside of the App Store; however, Apple's guidelines prevent apps from presenting this as an option.
Two of the industry sources say that the antitrust concerns focus on restrictions in the App Store. These include a prohibition on advertising in the app that the company is on other platforms, a ban on marketing in the app that consumers can also buy directly from the company's website, and a ban on linking to a company's website from within the app. These restrictions apply to all apps, not just music streaming apps.
Antitrust lawyers are reportedly split on whether Apple's policies violate antitrust law. Some feel as though Apple's rules are undoubtedly aggressive but still legal. Those critical of Apple may be looking for the FTC to use Section Five of the FTC Act which prohibits "unfair or deceptive acts or practices."
The FTC has yet to launch a formal investigation. We'll let you know how the situation progresses. Please follow iClarified on Twitter, Facebook, Google+, or RSS for updates.