I would agree. I am up big on 1 site and off the map on the other. I optomize each exactly the same. I could not figure out why they were both climbing at roughly the same pace and one could totally disappear. The one that dissappeared has a domain pointing to it that I bought so no one else could buy that domain. I only use one domain for the site as far as promotion goes and I rank high for allins.
I got killed in November on my main site, then came all the way back then some - only to just take about a 50% dip starting last week. I can't figure it out at all. It just can be depressing - but it makes me realize I have to do better across the search engine world, and that to rely on just Google is dangerous to your personal economic health.
This whole scenario reminds me so much of what happened last year, in the aftermath of "Florida" ... At least there was an end (rather a long respite) from the madness to that toward the end of April 2005 ...
I share all the points you mentioned, i have suffered the same issues as you and i narrowed it down to the same 301 and duplication issues.
When i run the site command my homepage is only ranked 112 out of 441 pages. It is slowly creeping up as we make minor changes to the site, but it isnt really good enough. My site totally dominates msn and yahoo, i know google is a different search engine but being on page 7 for google and page 1 for the others highlights some drastic differences. The drop came at a time when i was making no changes to the site.
If you want to sticky me with your site details i will send you mine and we can try to create a timeline of what happend on each site and when. lets see if this is permanent or if things will iron out!
I am up big on 1 site and off the map on the other. I optomize each exactly the same.
I have seen a similar effect. Before BD, I had two sites that were doing quite well in Google. Both sites are cross-linked with each other, use the same exact template and use the same SEO techniques.
Yet, two weeks ago one of them dropped off the map on Google. All pages are indexed but it has dropped 100's of positions on every keyword (even for 4 word keyphrases that no one else is targetting). The especially odd thing is that the site is an authoritative site on the subject and easily one of the 10 best sites on subject.
A while back, I did discovered an odd thing about the site. For days after the site dropped in Google, doing a link:www.example.com would return results but link:example.com would return none. Eventually, it quit doing that and the site did rebounded slightly. But, I still recieve less than 5% of the traffic I was seeing.
It feels to me like BD is broken. The SERPS in my sector look like crap.