Let's start with a definition of echo chamber.
That first part of the definition is key: "a room with sound-reflecting walls".
Everyone lives in some form of echo chamber. We're only human, after all, and we can't know, understand, or process everything. So we can only see one segment, one sample population, at a time. And since like minds congregate, that sample population will likely share similarities that the bulk of people don't.
Case in point: Self-publishing.
I work with self-publishers. I self-publish, myself. I know several folks who are selling copies in the thousands (or higher)…but I only know a handful of people who own e-readers. Most of them (the few people I know with e-readers) have tablets, which they use more for movies or TV than for reading.
My friends who read a lot? Don't have tablets. Most don't even have ways to really read an e-book unless they want to put it on a family computer (that they don't get much time on). These friends are all still heavy users of the library.
So if I look at the people I know in person, e-readers and e-books are going nowhere fast (my own personal Nook Simple Touch and e-book use notwithstanding). But if I look at the people I work with online, e-books and e-readers are taking the world by storm, and print books are going by the wayside.
The question then becomes: Which of those echo chambers jives with reality?
Obviously, considering they jive with my reality, but let's think about this a moment. Not everyone has a smartphone, in-home Internet, or even a computer or an e-mail address. That is pretty much an entirely separate segment of the population from the ones who have all the latest tech and have money to burn on e-books. Some folks literally don't have two pennies to rub together.
It's different audiences.
And that's what people tend to miss, when they're looking at reality though the lenses of their echo chambers. Just because you don't know anybody with a Nook e-reader doesn't mean nobody has one. It doesn't even necessarily mean that they're uncommon. It just means they're uncommon in the population wherein you hang out.
Now, it can be true, that the opposing echo chamber is tiny and insignificant, but any one of us can't really know that. Knowing it would require a worldwide survey of every person on the planet, which is impossible. We can suspect a viewpoint or situation is rare—among population types that we're observing, at least—but we can't know for certain.
For a religious example found in Christianity: Should people be baptised as infants (infant baptism), or only after they make a confession of faith (believer baptism)? (Note for any readers who don't know: Baptism can be performed by a sprinking of water or with immersion. The latter form isn't practiced with infants, so far as I'm aware, for reasons I think are obvious.)
To answer the question, infant baptism may be the most common practice worldwide, but popular evangelicalism practices believer baptism only. (Note that at least some denominations practice both: If you're born in the church, you're baptised as an infant; if you come to the church later in life, you're baptised as a believer. Practicing baptism this way stems from the belief that baptism is the New Testament version of circumcision. The believer baptism + immersion comes from believing that baptism is meant to symbolize death, burial, and resurrection.)
If a person grows up in a specific denomination of Christianity that practices one or the other, their personal echo chamber will tell them the other is uncommon or unheard-of, even when it's not the case.
As another example, consider the legality of first cousins marrying. I live somewhere where it's legal and not unheard-of. But I didn't even know that until I happened to meet someone who was one of those married cousins; and once I noticed it, I spotted more.
Why do I bring this up?
Because I not infrequently see echo chamber panic and rhetoric coming from people, about a variety of things. People get worked up about something—Oh, noes! The echonomy's tanking!—and panic, which only makes things worse for everyone. When the echo chamber contains outright misinformation, it can be even scarier—because the echo chamber riles people up and gets them to do things under the assumption the misinformation is valid.
Echo chambers exist. Keeping that in mind can help a person stay balanced rather than bending like a stalk of wheat under whatever way the wind blows.
What are your thoughts on echo chambers?