Update: Apparently the other update people are experiencing was a new Panda update. Google transparency at its finest.
As you probably know by now, Google's Matt Cutts announced an algorithm change on Friday - the EMD update. The change was designed to reduce low low-quality exact match domains in search results. Cutts deemed the change "small" and tweeted about it as a "minor" weather report.
Based on all of the complaints we're seeing (you can read plenty of them in the comments of this article), it may not have been all that minor. Cutts said that the change affects 0.6% of English-US queries to a noticeable degree, and noted that it was unrelated to Panda or Penguin. Still, based on all of these sites claiming to have been hit, you would think it was Panda or Penguin.
Some webmasters claim to have been hit, but not necessarily on sites with exact match domains. So why would they have taken such a hit? Well, it's not news that Google launches various changes to its algorithm on a day to day basis. The company often gives the "over 500 a year" number. This time is no different.
Search Engine Roundtable is pointing to a reply Cutts gave to one person on Twitter about the situation, where he noted that he knows of one change that was also released during the same timeframe as the EMD update. Here's the exchange (with another interesting one about Google's struggle with quality thrown in):
@GregrySmith yes. 500+ algo launches/year mean 1-2 a day. I know of at least one other algo rolling out over same timeframe for example.
While it's not that interesting that Google launched another change the same time as the EMD update (again, it's common knowledge that Google pushes changes every day), it is interesting that so many people are complaining about being hit when the update Cutts tweeted about was said to be so small, and that many of those claiming to have been hit were not dealing with exact match domains. If another change had as big of an impact, a greater impact, or anywhere close to the impact as the EMD update, why wouldn't Google announce that one?
Meanwhile, we're still waiting on Google to be "transparent" about the changes it has made over the course of August and September, with its monthly (at least they used to be) lists. All of that combined with new updates to Google 's Webmaster Guidelines should be enough to keep webmasters busy for a bit.