Historically, just before the holiday season Google has mode algorithmic changes (Except last year). Though last year we saw lots of algo changes in adwords to identify thin affiliate sites. Around last week of October; this month we have seen ranking losses for some of the sites. We are not the only one but its been documented https://searchengineland.com/is-google-broken-sites-big-small-seeing-indexing-problems-53701 by some forums too.
Some of the other questions on the forums are:
Google all along has maintained that there has been glitch and it will be rectified soon.
A Google employee , John has posted answered to one of such queries as follows:
“Just to be clear, the issues from this thread, which I have reviewed in detail, are not due to changes in our policies or changes in our algorithms; they is due to a technical issue on our side that will be visibly resolved as soon as possible (it may take up to a few days to be visible for all sites though). You do not need to change anything on your side and we will continue to crawl and index your content (perhaps not as quickly at the moment, but we hope that will be resolved for all sites soon). I would not recommend changing anything significantly at this moment (unless you spot obvious problems on your side), as these may result in other issues once this problem is resolved on our side.”
I feel that Google is definitely testing new algo (Or may have already implemented the same). And it is threat as well as opportunity for every good SEO Company. We have already started analyzing the data to check why and how it is getting affected. We looked on forums as well as in processes of formulating hypothesis as well as testing the same so that we understand the new changes.
Our first (very early) assessment points the fingers to duplicate content and “Not that Good” site structure. Though , it is too early since the experiments are set and the results are awaited.
Another hypothesis that we will test is about Dirty Back links.
Our request to the web site owners is to not get panicky; if your site is genuine then a few SEO tweaks should help you to tide over the present problem.
Let us know if you want us to study your site and we will be glad to do so!!!!