I agree completely, I've noticed that even if they are not linked to, Google tries to crawl the folder itself which is why I now create an index.php file for each and every folder even if it's just for show.
Wasn't that some time ago? Has that been said again recently because I've noticed more references to advancements in dynamic URL indexing over the past year by Google.
New Theory - one thing I tested (only on one site mind you but it was quite dramatic) was the % of pages with long URLs that affected overall ranking of the entire site. I was toying with it after Google FINALLY started to remove all those search engine scraper pages from the top rankings on google.co.uk - their sites were entirely made up of long URLs because they were auto-generated spam pages, nothing else. I switched a 500,000 page site from over 90% long dynamic URLs to at least a third of that using a mod_rewrite and some PHP scripting. Rankings increased substantially across the whole site on Google (Yahoo and MSN were unaffected).
Which leads me to another question - why did you start this thread in "Google Search News" Brett? Something specific you want to share with us about a new patent Google have applied for recently?