Forum Moderators: open
If you run through PR on an appropriate Google directory page you will see what I mean.
Look up say "hotel" in any major city and you will see that a "good" PR is 4 to 5, an excellent PR is 6 and very few (I have not found any) have a PR of 7.
On the other hand if you are looking for "hotel guides" or similar you will find that a "good" PR is 5 to 6 with the odd 7.
By and large, as you would expect, the higher up the Google Directory tree you go, ie closer to the root (if that is not a contradiction in terms), then the higher the average PR on a directory category, and sites like National Geographic and Lonely Planet will get an 8.
So no point expecting an 8 if you are lower down the directory tree. Strive instead for an appropriate PR that will put you ahead of the competition.
I suppose if a site is depending on their positions in the directory trees for most of their PR, then what you say is probably true, but at this point, I really don't care about the directory links, they can add me if they want. I would like truely important sites to link to me, the directories are more effort than they are worth in my case.