After rumors that first Facebook and then Microsoft were in talks to acquire Skype, the latter announced that it has acquired the VoIP giant for $8.5 billion in cash.

Skype will be integrated into Microsoft devices and systems such as Xbox and Kinect, Xbox Live, the Windows Phone, Lync and Outlook, Microsoft said in a statement. The company has pledged to continue supporting and developing Skype clients on non-Microsoft platforms as well.

The deal, which was spearheaded by Microsoft CEO Steve Ballmer with assistance from Charles Songhurst, the company's head of corporate strategy, was completed Monday evening, AllThingsD reported earlier.

The acquisition is an expensive one for Microsoft. Not only is it the largest price Microsoft has paid for a company in decades, Skype is not yet profitable. Despite revenues totaling $860 million last year and operating profits of $264 million, the company lost $6.9 million overall, according to documents filed with the SEC. And the company carries $686 million in debt.

Much of the company's appeal rests in its largest user base of 663 million, 145 million of which use Skype monthly (Update: Microsoft says Skype has 170 million regular users), and 8.8 million of which are paying customers.

There is one clear set of winners here: Skype's investors. A group including Silver Lake, Index Ventures, Andreessen Horowitz and the Canada Pension Plan (CPP) Investment Board purchased the company from eBay for $2.75 billion in September 2009.

In August, Skype filed for an IPO but put plans on hold after Tony Bates joined the company as CEO in October. Bates will take on the title of president of the Microsoft Skype Division and report directly to Ballmer.