Here's one new piece of information which has been confirmed by numerous webmasters:
Since the 'rollback' to fix #6 glitch my site dissapeared back to the sandbox but still shows up well on all the other DCs ....[Google] has discounted all links with less than 6 months of age.
Others, however, dispute the claim:
...this can't be the case. 6 months ago my pages were #9 and dropping in a specific search term. 6 months ago our link profile was abysmal.
One webmaster notes a "significant" drop in traffic since January 30th.
Another notices that Canadian results are differing from US results and has tested the theory with a proxy server.
Perhaps the strangest revelation of all is a weird caching issue:
I have most of my pages not indexed due to redirects (aka se friendly URL's), and my cached index page is that of another site completely which has nothing to do with me.?
Nobody can reproduce that, however.
On that note, I noticed that I did a site: search using a specific domain and a result came up that had no association at all to the domain I queried. I tested this a few weeks ago and then again just a few hours ago and the problem remains. Strange.
Forum discussion continues at WebmasterWorld.