It looks like the latest algorithm update coming from Google’s search engine was meant to diversify the different domains shown on the first page of results.
There were a few complaints about the same domain being shown on the entire first page for some results so this update was rolled out throughout that strange week of traffic starting around August 28th.
Here’s an example shown by SearchEngineLand here:
But for some reason the update hasn’t had the wanted effect because it still shows the same results here.
Matt Cutts also tweeted about the update:
Just fyi, we rolled out a small algo change this week that improves the diversity of search results in terms of different domains returned.
We’ll see if this is still an ongoing update and if it will actually fix the problem they want to get rid of. I still have some sites bouncing back and forth doing the usual Google dance, but I am seeing some improvements with multiple domains being on the front page. I’ll keep you updated once I hear more on this.