I myself have begun to think that a higher standard of friendship is needed in social media. Something like Twitter, where you can follow anyone unless they actively block you, makes more sense where engagement is limited, like how selecting a TV channel to watch is largely a one-way experience.
I would love to see a social network demand a higher standard of friendship from a user before other users are allowed in their network - based on something more than reciprocal button pushing, so kind folks don't feel compelled to accept a friend request out of politeness. Snapchat may be on to something here, as you actually have to know the person exists before you can add them.
I don't know exactly what the answer is - ask compatibility questions, quiz the user about their history, analyze their current social networks for positive engagement - but I'm extremely curious about the possibility of a social network that purposely limits its own network effects.