Some social media sites have potential for content posted there to spread virally over social networks. The term is an analogy to the concept of viral infections, which can spread rapidly from person to person. In a social media context, content or websites that are "viral" (or which "go viral") are those with a greater likelihood that users will reshare content posted (by another user) to their social network, leading to further sharing. In some cases, posts containing popular content or fast-breaking news have been rapidly shared and reshared by a huge number of users. Many social media sites provide a specific functionality to help users reshare content, such as Twitter's retweet button, Pinterest's pin function, Facebook's share option or Tumblr's reblog function. Businesses have a particular interest in viral marketing tactics because a viral campaign can achieve widespread advertising coverage (particularly if the viral reposting itself makes the news) for a fraction of the cost of a traditional marketing campaign, which typically uses printed materials, like newspapers, magazines, mailings, and billboards, and television and radio commercials. Nonprofit organizations and activists may have similar interests in posting content on social media sites with the aim of it going viral. A popular component and feature of Twitter is retweeting. Twitter allows other people to keep up with important events, stay connected with their peers, and can contribute in various ways throughout social media. When certain posts become popular, they start to get retweeted over and over again, becoming viral. Hashtags can be used in tweets, and can also be used to take count of how many people have used that hashtag.
According to writer Christine Rosen in "Virtual Friendship, and the New Narcissism," many social media sites encourage status-seeking. According to Rosen, the practice and definition of "friendship" changes in virtuality. Friendship "in these virtual spaces is thoroughly different from real-world friendship. In its traditional sense, friendship is a relationship which, broadly speaking, involves the sharing of mutual interests, reciprocity, trust, and the revelation of intimate details over time and within specific social (and cultural) contexts. Because friendship depends on mutual revelations that are concealed from the rest of the world, it can only flourish within the boundaries of privacy; the idea of public friendship is an oxymoron." Rosen also cites Brigham Young University researchers who "recently surveyed 184 users of social networking sites and found that heavy users 'feel less socially involved with the community around them.'" Critic Nicholas G. Carr in "Is Google Making Us Stupid?" questions how technology affects cognition and memory. "The kind of deep reading that a sequence of printed pages promotes is valuable not just for the knowledge we acquire from the author's words but for the intellectual vibrations those words set off within our own minds. In the quiet spaces opened up by the sustained, undistracted reading of a book, or by any other act of contemplation, for that matter, we make our own associations, draw our own inferences and analogies, foster our own ideas... If we lose those quiet spaces, or fill them up with "content," we will sacrifice something important not only in ourselves but in our culture."
Social media are interactive computer-mediated technologies that facilitate the creation and sharing of information, ideas, career interests and other forms of expression via virtual communities and networks. The variety of stand-alone and built-in social media services currently available introduces challenges of definition; however, there are some common features: