It turned out that Facebook had changed the algorithm for its news feeds, in response to its users' complaints that they were being overwhelmed by updates from "friends" whom they hardly knew. The 600-million-member social network now filters status updates so that, by default, users see only those from Facebook friends with whom they've recently interacted—say, by sending a message or commenting on a friend's post.
For now, the best Mr. Pariser can hope for is to educate readers who don't want to live in a solipsistic subset of the Internet, especially regarding political matters. Just knowing that Google and Facebook personalize what you see, and that you can turn it off if you want—on Facebook, click Most Recent instead of Top News atop your feed; for Google, get instructions by searching "deleting Web history"—is a good start. "The Filter Bubble" is well-timed: The threat is real but not yet pandemic. Major news sites are toying with personalization but haven't rolled it out en masse. And in a test I conducted myself, I enlisted a handful of heavy Google users across America to search for "Bin Laden raid" soon after the event. The search results that came back were all nearly identical. To tell the truth, we were kind of disappointed.This is a battle between reduction in transaction costs versus increasing confirmatory bias.