bowdeni - 8:57 am on May 26, 2010 (gmt 0)
Ok I'll throw a couple of more things in.
The website I'm working on used to have a very similar link profile to the competitors, i.e. links on same pages (sidebar/footer... previous seo agency). In the past our rankings fluctuate with a reasonable level of correlation as one would expect. Since we've worked on the website, we've been removing such links and creating out own link profile through content creation and distribution.
I mentioned that our ranking fluctuations were similar, well the drop our competitors had since late April marks the first shift away from the correlation. We haven't had the same (big) drop they had. (Maybe as a result of shift from sidebar/footer links to content, but many other variables involved.
We have dropped a little too. . We have our own problems too, so it's hard to put these things together and draw any correlations, but perhaps someone else will analyse something here.
Going back a month or so when many in the UK including myself were being served different indexes from DCs, I had an indicator I could use to tell apart the two indexes. In Feb I had a trailing slash on a popular on URL, and we changed the preferred version to non trailing slash. Google quickly indexed the non trailing slash. With the caffeine results however, it drew on the older slashed version but only for a week or so.
In the past two weeks, I've only seen the trailing slash version in the SERPs, indicating to me that the results are a little old, but hey, only hunches!