You know it is really great to have a near monopoly on search where how the "market" works is totally secret. Well mostly secret

! I think one of Google's real strengths these days is its ability to change to fight off most of the spam in its index. It has also been very effective in putting most SEO/webmasters in a "cloud" of information or misinformation. One such tool that it uses is PR or Page Rank.
Here are a couple of good examples of how the majority of SEOs and webmasters are so fixated on it:
http://www.seounique.com/blog/google-have-updated-page-rank-in-secret/
http://forums.digitalpoint.com/showthread.php?t=1105886
There are of course many threads on PR - why a site has gone up or down. White bar, gray bar. When the next PR update will be?
In reality, for the most part you should ignore PR. There a plenty of pages and sites that I have with low PR, no PR or even grey bar PR and you know what the pages still rank. And most still don't get that visible Page Rank is snapshot in time and usually is a lagging indicator. Don't get caught up in the hype. PR is just once indication of how one's site is doing. Continue to focus on good content, marketing your site and adding more value to your website visitors.