But wireless companies are quickly learning that data service can be a strong revenue driver too - good news for services like Skype and rival Google ( GOOG, Fortune 500) Voice, which are starting to be embraced.ĮBay bought Skype for $2.6 billion in 2005, only to sell it four years later for $2.75 billion to an investment group led by private equity firm Silver Lake Partners. Mobile providers had been hesitant to allow the service to be used on their networks, since Skype users would not have to pay the wireless network for the voice minutes used. Skype made headway when it landed a deal with Verizon Wireless ( VZ, Fortune 500) this year. In the filing, the company said it had achieved 'significant global scale and user growth,' but 'the penetration of our connected and paying users is low relative to our market opportunity.' Still, Skype said an IPO can help it do better. Paying users, though just a fraction of the overall user base, jumped 23% to 8.1 million from 6.6 million a year ago.

This year, the company has generated more than $406 million in sales, with 560 million registered users - up 41% from a year earlier.

Since EBay ( EBAY, Fortune 500) sold the company in September 2009, Skype has done very well.

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