"[This] is a transaction between the application vendor and the customer, while Google is just acting as a payment processor and delivery channel," he said.
But other privacy experts say the practice puts privacy at risk. "Supplying personal information to apps vendors is invasive in significant ways because of the way the information could be used, shared, and possibly monetized, all within the online environments in which they are used," said Rebecca Herold, CEO of The Privacy Professor. "[Apps] can also link to so many other entities in ways that other vendors of software you download onto your hard drive do not, and in many cases cannot."
Herold said Nolan is being "completely reasonable" to assert that users should be notified by Google Play that their information is going to the third-party developer. "Providing clear and conspicuous notice for how a site is sharing information is a basic, internationally accepted, privacy practice," she said.
Ben Edelman, an associate professor at Harvard Business School who has exposed privacy violations in the Google Toolbar and on Facebook, notes that Google informs those buying magazine subscriptions that their information, including "a unique identifier," is being shared with the publisher. "But Google says nothing similar about ordinary app downloads," he said. "In this context, a user would reasonably conclude that installing an app does not share name, email address, or other details with the app developer."
"Part of the rationale for buying via Google, in a marketplace Google purportedly supervises and runs, is to get protections including trust and privacy," Edelman said. "Google has been quick to emphasize those benefits when it suits them -- touting Google Checkout's ability to withhold user details from a merchant. It would be disingenuous for Google to disavow those benefits now."
Even if Google Play's Terms of Service puts the responsibility on developers to notify users that their information has been shared, Herold said that does not let Google off the hook. "What is Google doing to ensure the vendors are actually following through?" she asked. "Do they actually review the notices that the vendors are providing to the apps users? What will they do to vendors they determine are not adhering to the Terms of Service? Will they cut all ties with them, or turn a blind eye? Also, how do they define 'legally adequate privacy notice'?"
Samantha Murphy at Australia's The Age quotes Chester Wisniewski, a senior security advisor at Sophos, who observes that "users who buy something with Google Play are probably assuming they are doing business with Google -- not the developer."
Wisniewski said he saw no reason for panic, but it is a worry. "It's probably something Google should revisit," he said. "A cybercriminal could create an app just to get data, and that is what Google should want to avoid."
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