Changing the number of results to 100 in Google's settings page makes this more obvious: only 35 results for [cnet].
While the duplicate filter is not new, it was used to hide results that were redundant (for example: the same press release published by multiple sites). It's hard to believe that Google can't find more than 117 relevant results for [Google], 120 results for [Facebook], 86 results for [YouTube], 75 results for [Yahoo] and [Wikipedia].
When you search for [Yahoo], Google returns a lot of results from yahoo.com and Google's duplication filter stops showing results because they appear to be redundant. There's a conflict between two opposite principles: showing diverse results and showing many results from the most relevant sites.
Here's a page of almost identical search results that probably triggered the filter:
Another issue is that there are many spam pages, irellevant results and pages in foreign languages. Here are some examples for [Amazon]:
Some irrelevant results for [YouTube]:
Google needs to fix this bug and show more diverse results.
{ Thanks, Joren. }