I think it's time to clarify something here:
PageRank and PageRank Toolbar, are two different pair of shoes. What is not accurate is what you see in the
green PageRank toolbar. Andy Steggles of SitePR Tracker mentioned that the Google PR Toolbar is not accurate, not the Google internal
PR calculations.
Andy Steggles said that it is an indicator how Google perceives your web site. It is very valuable information to
look at it, but it doesn't mean everything. When all things are equal in the search results, the one with the higher
PageRank, is going to rank higher than the other page that has a lower page rank.
So does that mean that it is not valuable and important to you? For me it is. When I am done with my on-site optimization,
which my competition might can do so good as myself, then I am concerned about PageRank so I can rank higher than them.
Another issue is, that duplicate content is a killer (ie if you have content on your pages that is duplicated elsewhere on
the web, don't be surprised to see your PR dropping).
One fact is, that for example if you have on those duplicated pages a certain PageRank value linking to other pages or
sites of yours, it is obvious that you loose PR. To make this dummy proof, you are loosing backlinks. Or if a site with a
certain PR value linking to you have been banned or his PageRank value have been decreased,, there you will also have a
loss of PR.
Other facts might also be in the game, but so far I have no further information to backup about that.
Video of Andy Steggles with Mike (Admin of WPW):
http://videos.webpronews.com/2006/12...e-of-pagerank/