To Google, PageRank is just one of many tiny factors that make up the algorithm that determine the ranking of a website. To Webmasters, it's a magical green bar that can mean the difference between anything from bragging rights to $100 for selling links.
The PageRank most Webmasters refer to is the Toolbar PageRank and whenever you visit a page on the Internet, it gives a ranking from one to ten. However, on more than one occasion Google have stated that this ranking is so unimportant that they plan to remove it from the Google Toolbar.
Not Regularly Updated
The thing to remember about Toolbar PageRank is that it is a snapshot of how Google saw your site as many as 4 months ago. PageRank doesn't change regularly; it's only done when Google 'exports' the data to the public domain. I've seen many stories how people claim to have gone from a PR0 to PR3 in just 30 days. This is not because they have found some new trick, but because it was a coincidence that Google exported the data soon after they started the promotion.
Similarly, I've seen Webmasters ask why their site is still PR0 after 3 months of promotion. The answer is the same as above; Google hasn't exported the data to the Toolbar in the last three months.
But why are Webmasters so obsessed with PageRank given that Google has already stated that they see it as so irrelevant that they plan on removing it from the Toolbar.
One of the big reasons is that I think it boils down to a huge misunderstanding of what PageRank is and how it works. Many people believe that if you have a high PR website (according to the Toolbar data) you will automatically get high rankings. That is not true. A PR1 website often outranks a PR5 website in the search engine rankings.
Other people believe that if you get links from high PageRank websites you will get better rankings in the search engines and while you may get a higher PageRank for your website, you might not necessarily get better rankings as PageRank is just one of many factors that dictate what ranking you get.
I think one of the biggest reasons Webmasters get obsessed over PR is because it's a kind of quantifiable validation that you are doing things right. Since many site owners are extremely competitive it's a way of quickly and easily comparing yourself with others and seeing how you 'stack up'. Maybe the simplicity plays a big part, anyone can understand that 6 is higher than 4 and therefore it is in some way 'better'. In other ways it's validation that your hard work is paying off, especially if your PageRank keeps increasing, and yet another reason could just be bragging rights as not many websites manage to achieve a PageRank of 6 or more.
But this validation is misplaced in my opinion. It doesn't take in to account traffic, sales, conversions and a whole mass of other quantifiable data that a business is interested in. At the end of the day, while a PR8 website would give me great bragging rights, I'd turn green with jealousy if you told me your PR2 website got 2,000 visitors a day, had a 24% conversion and makes over $50,000 a month! Now that would give you some major bragging rights!