Once again, webmasters are complaining about what may have been a major update from Google. They've taken to the Google Webmaster Help forums to express their grievances, although to be fair, it's not all bad for everybody. When sites drop, others rise. That's how it works.
Barry Schwartz, at Search Engine Roundtable, who wonders if it could be the "overly SEO penalty" Matt Cutts discussed at SXSW last month, points to 11 separate forum threads with complaints. There's definitely something going on.
Of course, in these situations, the Panda update is always mentioned. We've reached out to Google for more info. Sometimes they respond. Sometimes they don't. It will most likely be one of the generic "we make changes every day" kind of responses, and we'll probably have to wait until the end of April or the beginning of May to get the real list of changes Google has made.
The last time there was a known Panda update, Google went so far as to tweet about it. They know people want to know when this happens. That doesn't necessarily mean they'll tweet every time, but I wouldn't be surprised. This time, no tweet from Google so far.
For a refresher on the "overly SEO penalty" Schwartz speaks of, read the following:
Google Is Working On Making SEO Matter Less
Google Webmaster Central Creator Talks Google’s “New” Google Changes
New Google Changes: Really A Matter Of Mom And Pop?
SEO DOs And DONT’S According To Google: Mixed Signals?
Other things have been costing sites lately. For one, Google's de-indexing of paid blog/link networks caused a lot of webmasters to get messages from Google about questionable links. This week, Google sent out messages to 20,000 sites informing them that they appeared to be hacked.
If you're rankings have fallen, one thing you may want to consider is taking authorship more seriously (and that includes Google+ engagement), though even that appears to be having some issues on the tracking side.
Last week, we spoke with Dani Horowitz whose site, DaniWeb, has been hit by Google, yet again, after recovering from multiple iterations of the Panda update.
Not only does Google make changes every day, it runs even more experiments, with subsets of users. Matt Cutts recently talked about how Google runs 20,000 search experiments a year.
Even more recently, Cutts talked about what will get you demoted or removed from Google's index.