Apple is rumored to be looking at such a system also and is well positioned as a result of its iTunes Music Store, which already has credit card data from 200 million users.

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United heard increasing complaints from elite-level frequent fliers and users of its preferred credit card that not enough awards were available, spokesman Rahsaan Johnson said.

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Apple takes a 30% cut from sales of everything sold on iTunes. 435 million users have credit card information on file with Apple.

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But like other social gaming companies, Zynga allows users to speed up the process by converting real dollars from their credit card and PayPal accounts into the FarmVille currency used to buy virtual goods.

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Credit-card companies have long enticed users with an array of rewards programs, from airplane miles to hotel rooms and cash back.

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Users buying products from the platform will have a choice to pay through either credit card or other third-party system such as WeiboPay or Alipay.

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