pageoneresults - 11:57 am on Apr 13, 2011 (gmt 0)

I noindex,nofollowed, and robot.txt blocked all the thin content.

Hopefully one or the other? Googlebot will not see the noindex, nofollow if those documents are Disallowed via robots.txt. You have to use one or the other, not both.

In other words, since people can still visit no-indexed pages, does the Google algorithm include them in its evaluation of the overall content and quality of the site?

Yes. As long as it is just noindex. As soon as you add nofollow to the mix, they are dead end pages. Careful with the use of noindex, nofollow. Using just noindex is fine and recommended to keep documents out of the index. Not out of the equation, only out of the index.