Alot of webmasters and 'SEOs' alike ask tons of questions about why their PR has dropped, how they can increase it, etc., etc.
I'm here to set the record straight. Google PR IS a major part of your rankings. HOWEVER, the way everyone here uses the term (99% of the time) is in reference to the VISIBLE Google PR value found in their toolbar. This is a POOR measure of PR folks and should not be used in ANY discussion about rankings or loss.
What we know: Google Visible Green Toolbar is updated quarterly. The information in the toolbar is not only old, but it's only snapshot of the overall health of a web site. Basically it's a loose indicator of the value of the incoming links to that particular web site.
But even then it's inaccurate. You do'nt want to even base links (those you acquire) solely on this value. Case in point. I have a web site, 60 Yahoo! back links recorded, more in Webmasters. There are nothing but junky (but related) links. The links are PR3 or less (ALL OF THEM), HOWEVER, what we see is a PR 5 for the web site that is slightly more than a year. WHY?
TWO links from a subdomain from CNN. That's it. PR 5. Visible PR overvalued? Probably, but nonetheless, an example of how basing any web marketing decisions on visible google PR is flawed. This solidifies the case of RELEVANT and AUTHORITY incoming links, NOT LINKS BASED ON PR.
Never should you ask the question about HOW to increase PR. That's the wrong question. That's like asking how far a car can fly. You want to ask, "what's causing my slow rankings or loss? Can I get more links? Should I be investing in more cool content?"
DO NOT ASK, 'should I increase PR'? PR is a result of those two items I mentioned above. You cannot directly influence the stupid green toolbar value! You CAN influence the links you get and the content you provide. whew.
So what IS the green bar good for? Quite simply, buying/selling/doing links.
If you buy links you want more 'PR JUICE' and opt for 'higher PR'. This generally holds water for web sites higher than a PR 6. however, anything lower and you're shooting blanks. Reciprocal linking schemes based on PR are also flawed strategies. Why?
Take a look at the #1 web sites out there, the big PR 10 heavy weights, or anything over 7. They link to whoever regardless of green PR because it suits their VISITORS!
That's a good rule of thumb, however, I can sympathize with brand new web sites clamouring for higher PR links since at the end of the day, currently Google rewards those kinds of links.