Conduct a search at Google on the keyword yahoo and then click to the fourth page, you should see "In order to show you the most relevant results, we have omitted some entries very similar to the 35 already displayed. If you like, you can repeat the search with the omitted results included." Normally when you see that, Google is using its duplicate content filter to take out all excess and redundant search results.
There is an old thread on this topic at Search Engine Watch Forums.
