Where a mid-range smart-phone would consume about 100 megabytes of data a month, more advanced models like the Apple iPhone or Motorola Droid, with fully fledged browsers and access to thousands of downloadable applications, tend to consume over 500 megabytes a month.

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But the follow on orders have been experiencing longer delays, and the more advanced models of the iPad Mini with mobile data support joining Wi-Fi, have had their release dates pushed back.

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Facebook is considered to have one of the most advanced privacy models for its apps because it lists nearly every type of data sought and provides users with the ability to reject apps' requests for some types of data.

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