Simsi - 3:11 pm on Nov 23, 2011 (gmt 0)
On a very large site, I programmed prioritised navigation to users based on their keywords to make their path to similar information easier on the site. I can't predict the interests of those with no referal information so they get the default order which has historically resulted in lower page views (around 15%) and lower "goals" reached (11%).
Therefore it's probably accurate to summize that 11-15% of visitors don't get the best out of the site. I assume a large proportion of these will go back to Google and go to another site which means that the "relevance" of Google SERPS was diluted too. So as far as myself, the customer and Google go, I don't see any winners.