I don't. I've found that the really big stuff tends to filter to the top no matter what, so between Hubski, Hacker News, Reddit, Facebook, Twitter, etc I usually hear about the really big stories. If I don't hear about it in spite of my best efforts to not care, it can't possibly be that important.
I can't believe this is the top comment. "Can't possibly be important" if it wasn't on social media. That's sad to hear. Journalism isn't in great shape. But I hope that there are stories beyond the TPP and Bernie Sanders running for president (all I ever see on social media).
We must use social media differently. My social media is overwhelmingly dominated by Pluto this week. Haven't heard a thing about TPP in ages or Sanders at all. I'd also point out that it's a one way relationship. "If it's important, I'll see it without seeking it out" does not imply "if I see it without seeking it out, it's important".