[norhi999]

Because they:

a. Effortlessly gather people that have similar ideas but don't want to challenge them for their validity and only want peer approval, which they receive. It started mentioned recently mostly because of advent of simple and far-reaching communication means which exacerbated the problem that existed even before that.

b. Implicitly use such approval, clarification and repetition of the same ideas as key ingredients for long-term learning. That's why such communities are all too easy to radicalize, making vague assumptions and feelings into established worldviews, and becoming toxic or even aggressive toward out-groups and out-ideas.

c. Prone to become target for informational poisoning and manipulation as ideas are rarely challenged there.

d. Create and amplify skewed norms because they tend to miss on naturally occurring diversity of opinions.

[fargle]

well said.

now, the next step is - how do you identify whether you are in the real open world or just another, bigger, echo chamber with lots and lots of "like minded" folks who all think they are extremely open minded, to the point of congratulating themselves on it incessantly? (i can't think of any place like that...)

the answer is that if you are typing, it's almost always the later and if you are speaking to someone IRL it's the often the former.