6. Microsoft Buys LinkedIn For $26.2 Billion

Some people, at first, scratched their heads in June when Microsoft announced a deal to acquire LinkedIn, the social media network for professionals, for $26.2 billion. It was the biggest acquisition in the software giant's history and the price tag was a roughly 50 percent premium on the company's market capitalization.

But soon Microsoft's plan became clear. Integrating Microsoft's Dynamics CRM applications and Office 365 productivity apps with the information LinkedIn has on its 433 million members will provide a wealth of opportunities for the company and its channel partners to offer services that help business people develop contacts and recruit new employee talent.

Microsoft completed the acquisition on Dec. 8. In a blog post Microsoft CEO Satya Nadella wrote that the joining of the two companies will ultimately "help professionals transform how they work, realize new career opportunities and connect in new ways."