weird thing, my facebook fan page is now PR3 on google search for my product, yet my PR for my actual website is PR6 moved down for some reason, no recent changes, anyone know why it would be? if only bing was as good as google, i'm PR1 there =D
Duplicate content? That could one of the possibilities. Since FB has a higher PR period, its pages will get "preferential treatment" over your website almost always. But I am just guessing. Anybody's guess in this case will be just as good (or bad) as mine.
Sometimes even no change can bring down your website's PR and traffic. If the competition in your niche is constantly improving their websites in both content and functionality and you're not doing anything their ranks will go up and your will go down.
Sometime its happen that inner page PR is higher than main url PR but its very rare and was discussed on Google+ somewhere.