There is a fascinating and disturbing 10-minute TED talk by Eli Pariser, in which he explains how your favorite internet sources (Facebook, Google, etc.) are controlling the content you see, without your knowledge or permission. This is not a conspiracy theory, but is based on changes Eli has recently observed in his own internet results. He explains how and why this is happening, and why is it not a good thing.
In the middle of the talk, I was reminded of Lawrence Lessig’s 1999 book, Code and Other Laws of Cyberspace, which describes ways in which software implementations can subtly (and not-so-subtly) promote a particular agenda or position.
Pariser’s TED talk is at on.ted.com/Pariser.