But what's troubling about this shift toward personalization is that it's largely invisible to users and, as a result, out of our control. We are not even aware that we're seeing increasingly divergent images of the Internet. The Internet may know who we are, but we don't know who it thinks we are or how it's using that information. Technology designed to give us more control over our lives is actually taking control away.

Serendipity is a shortcut to joy.

Amazon could make recommendations on the fly, ("Oh, you're getting the Complete Dummy's Guide to Fencing? How about adding a copy of Waking up Blind: Lawsuits over eye Injury?")

At its worst, the filter bubble confines us to our own information neighborhood, unable to see or to explore the rest of the enormous world of possibilities that exist online. We need our online urban planners to strike a balance between relevance and serendipity, between the comfort of seeing friends and the exhilaration of meeting strangers, between cozy niches and wide open spaces.