Google used to include SermonIndex as a top result for other search terms that do not include the words "SermonIndex."
For instance, a search for "Leonard Ravenhill messages" used to include messages contained on SermonIndex in the top few spots. Now, SermonIndex is on the second page...behind a few websites that likely have less traffic.
This potentially has an immense impact on the number of visitors to the site. It is akin to the difference from advertising on the front page of a newspaper to the second page.
Oddly, while the search results for Leonard Ravenhill don't list SermonIndex until the second page, David Wilkerson results are listed as the #1 search return with Google.
Unfortunately, I have noticed the same thing with Bing.
I went to a local Microsoft Store yesterday and took the "Bing Challenge." You search for five things, choose the results which are your favorites (either Google or Bing) and see the results. I searched for SermonIndex, Leonard Ravenhill messages, David Wilkerson messages, A. W. Tozer messages and revival sermons. Bing results were similar to Google's in this regard.
I suspect that the algorithms used by these sites are altered from time to time. In fact, Google's "Panda" and "Penguin" search algorithm was changed this week.
http://www.examiner.com/article/everything-you-need-to-know-about-the-latest-google-algorithm-update
I will remain in prayer over this!