It all happened during this weekend, when some of us started noticing major changes with the Google search results and the rankings of our sites…
In short, no one is happy with this sudden and unexpected move. The webmasters are noticing low quality sites come into the search results as they are crawling the web to search their once high-ranked site!
Matt Cutts of Google put a post on the Webmaster Thread.
I think this was a short-term issue and things should be back to normal pretty soon (if not already).
What exactly happened? Matt elaborated later in the thread:
I don't consider those rankings indicative of anything coming in the future. Some data went into the index without all of our quality signals incorporated, and it should be mostly back to normal and continuing to get back to normal over the course of the day.
Yes, this was a bug as Matt said after giving reply to a particular question as to whether or not this was a "bug" or a "test." Matt replied, "nope, it wasn't a test."
It is really nice to see that the Googlers are coming to assist the webmasters to alleviate the concern.