In my opinion, todays estimation of the Pagerank algorithm should be reviewed. Now if we all put our heads together, we could have a good chance of success.
Consider the following statements:
1: Google DOES NOT care only for inbound links. This is referred to as "dumb" link popularity, and assuming that good inbound links will do all the job is wrong. The Googlebar is evidence of this. Users of the Googlebar have their traffic logged, and their recorded behaviour will
affect the Pagerank of the visited sites.
2: The quality of inbound links, however, is an imperative. Clearly, inbound links with Pageranks of 5, 6, or 7 will cause high PR for the site being linked. The higher the better.
3: Now is something left out? Is there more to the Pagerank system that has not been thought of. In my opinin - yes. Due to the fact that the Pagerank system is far more advanced that what is being referred to as "dumb" link popularity, the system itself will be relative. And the rankings will be relative. And it all boils down to the competetion; the number of sites regarding the search term.
A high quality site concerning a general and/or popular search term will not necessarily achieve a high ranking if linked from other high PR sites. This is due to "noise": the presency of many other competing sites. The site will probably be compared to other sites in the relevant categorie(s). Evidence supporting this is the fact that Pageranks can change both ways, and even without a site loosing any inbound links.
So here's what I think is important for link popularity:
-Quality inbound links.
-Quality content - this will attract visitors. Presuming some of these users utilize the Googlebar, traffic/popularity will be recorded.
-The number of competing sites - which in turn will have impact on reveived traffic due to what we can call "noise".
I think that todays estimation of the Pagerank alorithm is far too little complex, due to the fact that it has far too little data to build an analysis on.
Keep this in mind - the Googlebar is NOT a tool for which SEOs can use to view their Pagerank. The Googlebar is a tool made by and for Google and users of Google. And it is probably left out of todays estimation of the Pagerank algorithm.