Both of the web's leading search engines now use social data as a signal in determining search results. On a related note, Facebook uses my social network and engagement data to personalize my stream. And this often sucks. Not because I worry too much about my privacy, but because it promotes a fishbowl effect.
I recall a news story a few years back where conservative political pundits accused Google of favoring liberal content in search results. I have heard the same accusations from liberals. This is the beauty of near-universal search results. We as a society were regularly presented with views other than our own. As much as I am fairly comfortable with my political allegiances, I love that the web regularly exposed me to new thoughts and ideas. Google once exposed me to both sides of the story, not just the sides my friends were talking about.
Unfortunately the premise of personalizing one's search experience based on social data minimizes this broad exposure. If I wanted to know what my friends thought, I would ask them. But when I go to the web looking to discover something new, I don't want to see more of the same.
Here's to universal search. Without it, we may just have to trust journalists to cover both sides of the story.