If you think a little about search engines, you'll conclude they make popular sites even more popular. People are likely to find popular sites in the search results, they link to them and increase their popularity. This ultimately leads to a Googlearchy, a hierarchy artificially maintained by search engines. Arstechnica found a study called "Topical interests and the mitigation of search engine bias" that shows these conclusions are not valid.
"Traffic increased far less than would be expected if search engines were enhancing popularity. It actually increased less than would be predicted if traffic were directly proportional to inbound links. In the end, it appears that each inbound link only increases traffic by a factor of 0.8. The results suggest that the reliance of web users on search engines is actually suppressing the impact of popularity."
One explanation for this is that people already know popular sites and they want to discover other interesting sites. Another one would be that popularity is limited by the audience, so it can't grow infinitely.
"Our result has relevant conceptual and practical consequences; it suggests that, contrary to intuition and prior hypotheses, the use of search engines contributes to a more level playing field in which new sites have a greater chance of being discovered and thus of acquiring links and popularity, as long as they are about specific topics that match the interests of users as expressed through their search queries."
Search engines aren't the only way people find information, as is the case with viral content sent by email or instant messages. So until search engines find a measure for interesting content, next time you use search engines think there are a lot of great things on the Internet you've never stumbled upon. And visiting the same sites from your favorite closed circle won't help.