piatkow - 9:05 pm on Jan 1, 2010 (gmt 0)
Main thing you are missing - the object of the exercise is not PR it is getting people to the site to buy the product or click the ads. PR is just one factor. If the page does not contain the words that people will use to search then PR10 is useless. If it comes top for the key search terms then the PR doesn't matter.