Reps. Edward J. Markey and Joe Barton, co-chairmen of the House Bi-Partisan Privacy Caucus, have asked Apple for an explanation of recent changes in the company's privacy policy.

The congressmen are concerned over media reports that the changes suggest that Apple is collecting and sharing data containing the geographic locations of iPhone and iPad users.

"Given the limited ability of Apple users to opt out of the revised policy and still be able to take advantage of the features of their Apple products, we are concerned about the impact the collection of such data could have on the privacy of Apple's customers," the lawmakers wrote in a letter sent Thursday to Apple chief executive Steve Jobs.

Markey, D-Mass., and Barton, R-Texas, have asked Apple to respond by July 12. Apple did not return a request for comment in time for this writing.

The changes to Apple's general privacy policy was first reported Monday by the Los Angeles Times. The paragraph added would allow Apple and unspecified "partners and licensees" to collect and store user location data, the newspaper said. Users of Apple products would have to agree to the policy first.

Apple has been collecting location data since 2008. The difference now is that Apple has moved the notification of the practice from End User License Agreements of individual products to its general privacy policy covering all product, the Los Angeles Times reported.

The added passage reads:

"To provide location-based services on Apple products, Apple and our partners and licensees may collect, use, and share precise location data, including the real-time geographic location of your Apple computer or device. This location data is collected anonymously in a form that does not personally identify you and is used by Apple and our partners and licensees to provide and improve location-based products and services."

While the data is collected anonymously, analysts have shown that such data can be used to identify people based on behavior patterns. However, without the gathering of location data, applications dependent on the information, such as mapping software, wouldn't be very useful. How to balance the need for such information and people's privacy remains an open question.

Nevertheless, the number of smartphones with location-based services is growing dramatically. The number of smartphones with navigation systems supporting such services will rise from 81 million units this year to 297 million by 2014, according to iSuppli.

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