Brett Tabke, founder of WebmasterWorld, asked in a WebmasterWorld thread if Google is once again crawling and indexing new content discovered from referral logs? Let me quote his full question:

You can see that Google has indexed thousands of search results from the new WebmasterWorld search. Now, Brett just changed the url from newsearch.cgi to search.cgi.

What is interesting is that just yesterday I noticed that thousands of rustysearch results are now in Google. I believe this is new and I will try to get them out but it is an interesting coincidence. More details on RustySearch over here.

In any event, I am not exactly sure what is going on. That is why we have forums to discuss it.

Forum discussion at WebmasterWorld.