Social Median's news sources have, to date, come through "Snips", which are user generated notes, a lot like Tweets on Twitter, and "Clips", which can be done from any page on the Web, through the bookmarklet, or through submitting news directly on the site. As with other social sites, you can "Clip" other users news items, essentially adding your vote and sharing it to those who follow you, or make comments on the story excerpts. Integrating with Google Reader's shared items reduces the effort needed to add news, and Social Median parses the shared content to determine if it is relevant to specific networks, based on keywords, automatically making the shared news available to those following individual topics.
A recent item shared via Google Reader to Social Median
Unlike sites dedicated to showing the most frequently shared items, including Feedheads, RSSMeme and ReadBurner (See Disclosure), SocialMedian doesn't display a leaderboard for stories, focusing instead on offering personalized news and information on the topics you have selected.
Integrating with Google Reader's shared links removes the need to proactively share news to Social Median, cutting out the middleman, and undoubtedly increasing the volume of stories that are on the site. I expect the move to be good in terms of making the site more of a go-to for topical news, but also that it may result in fewer comments and clips per story.
You can see what I've shared to Social Median here: http://www.socialmedian.com/louisgray. Those from Google Reader are said as "Submitted by louisgray from Google Reader". My Google Reader shared links blog is here.