What do the SOCIAL people want out of their MEDIA?

What I am trying to outline in my title is that the people (the social aspect of social media) are what matters. I think that we can sit in the classroom all day and argue about what makes a great social media platform, but at the end of the day, the successful platforms are the ones that the users enjoy and feel are easy to use.  I feel like one of the best forms of research can be done by actually having people experience different social media sites and see which ones they like best, and which ones they find easy to use.  So in summary, I feel that yes, someone can and should start with a goal in mind, like how Twitter wanted people to share witty one-liners, but if people don't enjoy and understand how to use the social media, it won't be used and it will fail.