Social media, specifically microblogging networks like old Twitter, were uniquely effective at delivering near real-time breaking updates in ways that left older news delivery systems in the dust. I could do without the vapid comments, but this one aspect has real utility and I don't really know of a way to replicate that in other systems. I say this as an outsider that would only occasionally use the site to search for breaking news that hasn't hit other outlets yet.
My question is about where you draw the line on what constitutes a social network as the edges get blurry. Are comment sections social media? Are sites like Reddit and hacker News? Blogs? Blog networks with social features like Tumblr?