can I please ask the good folks on this list to provide their definitions of the term 'social media' as well? (in relation to SNS or in relation to 'non-social' media, if there is such a thing).
I'd rater compare Social media to User-generated content. UGC is anything that you can find on a platform that does not discriminate for participation. It should include, although it's odd, professional content made for YouTube. It would be called Social Media when the conversation is the message: people talking to each other though webcam on YouTbe make it a Social media; artsy indy films, less so. The difference with Mass media is that the poster doesn't have an unbalanced position towards its viewers (and explicit technical means, implicit authority): comments at the botton of a blog, or letter to the editor would be intermediate versions. Replies between blogs is social media.
The reason I ask is not merely academic curiosity. I have agreed to teach a class on social media for the first time in my school and I think it will help in positioning this class vis-a-vis other related classes if I can collect some thoughtful definitions of the term and get some idea for what people think it should include. I'll refrain from providing my own version here because I'd really love to hear your perspectives first.