There are a couple of issues with documentation... most notably that it DOES take a long time to write (at least to write it well) and is then generally copied unmercifully... so folks have to be doing it specifically with the mindset that this is OK and that they're wanting to give it away.  Another consideration is that this can also take the form of competitive advantage... ie. that folks prepare documentation in a style and with a look (examples) that suit the personalization of their own site, etc.  And all of that is great... but it does account for some of the challenge.

That said, an awful lot of folks do rise to the challenge and create great tutorials and helps, etc.  We're also working on a lot of things... but moving towards facilities for better user AND developer documentation is one of them.  As the guy who did the original 3.0 guided tour... I can tell you that something like that represents about 3 weeks worth of man effort... and it is not even a complete work (only spanning basics and a few modules).

When we have a few additional resources under our belt (like a Wiki which is currently in the Release Tracker), enabling community contribution to a larger "managed" effort may become a reality!

Scott Willhite, Co-Founder DNN

Sorry, not actually addressing your question... just waxing philosophic *grin*

The guided tour, though dated, is still pretty helpful: http://www.dotnetnuke.com/guidedtour
(If someone out there reading this would care to update it for 4.x and contribute it back... the source files are downloadable there)

Our Online Help is excellent, though very 1,2,3 oriented as opposed to "here's how/why" oriented:
http://www.dotnetnuke.com/tabid/787/default.aspx

There are also many other sources of community supplied documentation which I will let others push you toward.  I was simply recognizing this as an area of continuing development that will begin to improve rapidly as soon as we (soon...) provide some centralized facilities for capturing these contributions.

Scott Willhite, Co-Founder DNN