ソース２：Social Media Goes Mainstream
Wikipedia of course has the most easily accessible definition of social media, describing it as "online tools and platforms that people use to share opinions, insights, experiences, and perspectives with each other. Social media can take many different forms, including text, images, audio, and video. Popular social mediums include blogs, message boards, podcasts, wikis, and vlogs." The key here is that people are the ones that use and control these tools and platforms instead of organizations and large institutions. Further, I would add to this that social media platforms tend to work best in networked environments , particularly on the Web, but also behind firewalls though to a lesser degree. Why is the networked aspect so important? Primarily because it's a powerful democratizing force due to its pervasive, low cost nature; anyone can get in the conversation with only a small investment of their personal time and access to a network. And since communication is essentially free over computer networks today, combining an architecture of participation powered by network effects makes social media platforms almost certainly the most powerful form of media yet created.