Thank you all for your comments and insight into this issue.
I'm currently looking at the "tag" method of filing things and, for a small 4 person family, that is certainly workable (I guess if you can remember the tag order !!), but for larger organizations I still feel the nested folder method has merit, not least of all reigning in my rampant OCD..:-) After all, NimbusNote can do it (competing product) and so can OneNote (after a fashion)...
One of the things I use Evernote for (apart from tax, and my ham radio hobby) is the tracking of issues reported and solutions in my daily work in a Bank's IT Department - our current "documentation" system is an ancient POC called eRoom, which is heavily folder-based - it's a structure that people understand and are comfortable with, which is the other reason I want to do likewise in Evernote - if I can prove that Evernote will do the job more efficiently and effectively than eRoom, I stand a better chance of having it adopted across the board (we have OneNote as part of the Office suite, but for me it just doesn't have the same flexability as Evernote).
If Evernote had some sort of a "query language", where you could define (and save) queries on tags on both an individual and global basis then maybe the "one big pool of information" approach would work, but it would require some massive re-education of people's thinking - the whole folder paradigm is just more "logical" to most.