Here's a nice stat, from the latest Pew report on social media: "Some 38 percent of social networking site users have discovered through a friend's posts that his/her political beliefs were different than the user thought they were."
That's noteworthy not for the 40-ish percent of people who were surprised ... but for the 60-ish percent who weren't. Here's how Pew presents its question and findings in more detail:
We asked all the SNS users in our survey whether they have ever learned that someone's beliefs were different than they thought based on something they posted on the sites. Some 38% of SNS users said they had made that discovery and 60% said they had not.
In other words: A positive answer to Pew's question would require that, over all the months and years you've been on Facebook or Twitter or wherever else -- and among all the people you've encountered within those social networks over the course of those months and years -- you have encountered one person whose politics have surprised you. Just one.
The fact that not even 40 percent of Americans have had this experience is, in that light, itself pretty surprising.
So why are things this way? It's an open question. It could be that social media relationships, often being distant and impersonal, mean that we don't know or care enough about our fellow users' politics to be surprised by them in the first place; it could be that, as social media become more and more culturally prevalent, we're becoming conditioned to talk about politics, and other contentious topics, less and less within their borders. (The professor Pablo Boczkowski makes this case about the workplace, arguing that the relative political diversity of the typical office discourages people from talking politics at work.)