When you expand the equation, (take a taylor series expansion, for example), the initial subtraction becomes a delta, which is just added to another gamma. Basically, the inital subtraction doesn't really matter. All it does is set a minimum pagerank saying that the page does, indeed, "exist".
And yes, I forgot the first key set of parenthesis in my equation; however, it really wouldn't make any sense withouth them.
Distribute "d"; it doesn't really matter if it is .15 or .85, all that matters is that its less than one. This is where our understanding of how the equation works diverges. If you DO distribute "d" among the individual pages, THEN add, you get a decidedly different result from ADDING and then applying D.
Now, from Marcia:
Extend your thinking of pagerank into a two-way street. Pagerank has a sufficient effect on search engine indexing and ranking. For example, each week I add 50 or so pages (articles) to my non profit website; these are all indexed by google by the following monday. In an manner of speaking, google has created links for these pages of a designated "1" from its own indexing process. This pads the number of actual pages in the website; possible is a pagerank increase through this.
Now, develop a plan to do something like this on a regular basis. Do you ever notice how some sites aren't regularly re-indexed? That is, new pages sometimes take a month to be added to the google index for them? This even happenes on PR6/7 sites without much content change.
However, sites that DO have content development and DO have an intital pagerank see their pages indexed more quickly. I have first hand proof of this, comparing exact changes to a PR7 and a PR4; one gets the changes indexed in a few days, the other, more than a month. (No external linking present on any of the new pages; the PR7 being updated weekly, the PR4, monthly).
In my mind there is a premium placed, however hard it is to focus down upon, on regular development; and this is seen directly through indexing and then, second hand, through pagerank.