5. Skype
Wait, what? Skype is a Microsoft product? As of May 2011 Microsoft purchased Skype, and started phasing out Windows Messenger in favour of the far more popular and useful VOIP messenger. But that didn't help Microsoft, or Skype for that matter. I don't know about major businesses, but I do know that most people use Facebook, or their phones. There are exceptions, like people who have relatives in different countries, however Facebook, Twitter, Google+ etc have becoem the household names of social sharing. In an effort to remain relevant Skype has gotten into bed with Facebook, powering video chat between Facebook users, however there are more feature filled options out there. For messaging, Facebook is the way to keep in touch or for Google users, whether Apps or normal, Hangouts (formerly Google Talk) provides both messaging and video, supporting up to 10 people for free, while Skype only allows two. Contenders: Facebook, Hangouts