This may be funnier than anything posted but here goes....
I read a free pdf download from a fellow and it was talking about no following your links to avoid sending
PR to non-important pages on your site, that visitors should see but that didn't need all of the
PR flowing to them. (at least that's my understanding was)
I have about 100 item pages that were all indexed and had PR3. My Index page was PR4, Sections PR4 and item pages PR3. Many items were landing pages too. These items had to reference the "fitting guides" to see if the item was recommended for their equipment. Every page needing this fitting info (about 100 items) have a bulleted list of features.
On the last bulleted feature entry I had some text like
Be sure to check our "fitting guides" (internal link to guides) to be sure of a perfect fit.
I decided that my fitting guides didn't need all of those internal links (for spiders) and put "no follow" attribute on each link to the fitting guides. Maybe or not, this was followed about 30 - 45 days after, by a a toolbar update and my home page stayed at PR4 and the sections dropped to PR3 and items to PR1 or PR0 or dropped "no cache" when requested through the toolbar. I also lost my dozens of 1 & 2 (doubles) for the niche's SERPS, they were dropped to 3 & 4's under my competitor..arrrgh.
I took off all of the no follows and have seen in the past 2 weeks, that I've reclaimed some of them back to 1 and 2 position but only about 1/3 of the losses. Oh well, many would be happy to have double 3 & 4 search listings for their terms but not after you've had 1 & 2 for years. I think it had to do with the no follows. Now I don't have that important link to the fitting guides on the item pages anymore either - don't know what to do about that?
If Incrediblehelp reads this - it isn't the site I PM'ed you about. This is my money maker and dropping former landing pages (PR0 or Gray) and reduced
PR has hurt, not badly but surely a noticeable amount.
BOO - to "no follow"! I should have kept my hands in my pockets instead of writing 100 no follow internal links!
Or, it could have been something else - but nothing changed for years (in regard to internal linking) in my site's architecture.
Just an experience I thought I'd share.
cz