The comment section, submissions themselves, upvotes, and the user profiles - some of them even reaching celebrity-like status, for better or worse - are social elements in my eyes. And yes, I would also classify the usenet and mailing lists as social media. As for Wikipedia, maybe certain parts.

On the other end you have traditional media with fewer social elements and a limited number of content publishers: the press, books, television, radio, and read-only websites.