Blogging echo chamber refers to the phenomena of echoing news, events etc. (usually time-sensitive content) that other blogs have written. This creates a virtual echo chamber, where you read similar posts everywhere you go.
Examples of these include similar posts when Microsoft first announced its intent to acquire Yahoo. Every other blog you visit would be flooded with rumours, predictions and news of the acquisition attempt.
Not only does this inundate the reader with useless information, but severe duplicate content issues may also crop up. Even if you have described the events in own words, the content will be quite similar, and that spells doom for your domain in SERPs. Google not only drops those particular posts from the search results, but also other original content (since they are all part of the top-level domain).
The obvious winners in these are the big blogs who break stories, watch traffic pouring in and links coming in slowly. Blogs like TechCrunch and ArsTechnica often get inside scoops of upcoming events, and post them to their blogs.ADVERTISEMENT
How does this affect non A-listers?
The first result is that the others have to hurry and post like crazy. This leads to overall decrease in quality, not to mention a complete waste of time. The posts will rarely justify the results (which are next to none), hence demoralizing bloggers. The number of new bloggers who post news and then quit once they realize that news blogs cannot succeed easily, are high.
A better idea for them would be to post 2 or 3 original posts that add value rather than contribute to the echo chamber. I had actually started this blog as a tech news blog, and then converted it into non-news posts completely once I understood the facts.
What is the end result for blog readers?
Blog visitors will often find content similar to those on large blogs. Again, smaller blogs will only be affected, because hot news posts are posted by larger blogs. Visitors who have previously read news posts, will have a bad impression when they see the same thing on smaller blogs. That is the fastest way to drive visitors away from your blog! (which you would not want).
I personally hate news blogs that only recycles content, and never visit such blogs again. TechCrunch and other large blogs are an exception, again due to the reasons mentioned above – tracking large blogs can give you more, if not most of the news in one place. To me, that is better than subscribing to hundreds of smaller blogs. Digg and Techmeme are reliable sources of news if you want them at a single place too.