DeeCee - 8:31 am on Feb 28, 2012 (gmt 0)
It all comes back to one thing. Create web-sites for users, not for Google. (Blasphemy, I know).
Trying to SEO a site, especially a larger one, to suit Google's latest algo changes becomes a full time job, and still has no guarantee of working short-term or especially longer-term, since content from competing sites play in as well.
If you have a large number of pages, and change the structure, titles, links, to fit Google's latest algorithm or opinions on how they would like to present our content on their site, by the time your pages have been refreshed, the "rules" will have changed again, or Google will have entered a new business area that shows up prioritized on search pages.