The echo-chamber is described in the "about" section of Hacking Christianity:
We can choose which channel to always watch (Fox News or CNN, etc), we can choose which blogs to read, we can even customize our news and search filters to always come from the same avenues or philosophies.
The digital age has made living in an echo-chamber a very easily achievable reality...an echo-chamber that often has its mind made up already about Christianity in general, and individual Christians in particular.
On wikipedia, the echo-chamber is evidenced in the media as wel:
Metaphorically, the term echo chamber can refer to any situation in which information, ideas or beliefs are amplified or reinforced by transmission inside an "enclosed" space.For example, observers of mass media journalism describe an echo chamber effect in media discourse. One purveyor of information will make a claim, which many like-minded people then repeat, overhear, and repeat again (often in an exaggerated or otherwise distorted form) until most people assume that some extreme variation of the story is true.
Bill Bishop on the Daily Show
(4:52) Bill Bishop: People choose to read stuff, live places, look at things that reinforce their own beliefs. It doesn't matter whether there are two newspapers or 40 news channels, you are gonna pick the stuff that reinforces what you believe.