What is Social Media?

"Social media" is undoubtedly a broad and loosely-defined term. Wikipedia's article on social media defines it as "the social interaction among people in which they create, share, or exchange information and ideas in virtual communities or networks." This definition, albeit a brief one, provides a set of criteria for social media:

1. Social interaction among people is a definitive characteristic of social media;
2. It involves the creation, sharing, or exchange of "information and ideas"; and,
3. It focuses on the spread of information and ideas throughout virtual communities or networks.

It is then perhaps reasonable to postulate that any medium which exists online, provides a platform for social interaction among people, and lends its focus to the creation, sharing, or exchanging of information throughout the subsequent communities which would then form around such a platform, would qualify as social media.

What differentiates "social media" from other forms of media is its emphasis on interactions between people. A dedicated site may introduce other elements (commercial, for example), but they will always be built around the impetus of networking among users, and the proliferation of information throughout the communities built by these users.

Social media has become so ubiquitous, that elements of it have begun appearing even on non-social media sites, such as in the form of comment sections, forums, and the option to "like" a magazine article.

Having skimmed over Wikipedia's list of social networks, and the list of services supported by ShareThis, I've found that virtually every site or service listed, from Facebook to OUTeverywhere (an LGBT community) to WAYN (a community concerned with travel and lifestyle) to Digg, is dedicated to the creation of a community of people who share similar goals, interests, or lifestyles, or who otherwise wish to "network" with others online. Some sites are characterized by more interactivity than others, and some by less of a focus on sociability than others.

Speaking of Wikipedia: it is itself ostensibly a social media platform, especially since it is edited and moderated by a community of users. All of Wikipedia's content is, essentially, user-generated, and it is frequently modified and discussed on forums by users.

Some examples of "clearly social" media include Facebook, Twitter, Instagram, and Tumblr. These sites are unambiguously focused on the "social" aspect of social media - interaction among users. Examples of "clearly not" social media include strictly commercial sites which do not allow user commentary. Without any semblance of user interaction, social networking or user-generated content, a platform cannot be considered a social medium.

Links:

http://en.wikipedia.org/wiki/Social_media
http://www.sharethis.com/publishers/services-directory#sthash.3kLlGeLJ.yVSSSMvH.dpbs
http://en.wikipedia.org/wiki/List_of_social_networking_websites