Is that what you're asking?
But, one other thing I would strongly recommend is to never create extra or redundant folders unless they really add a lot of value to your site usability. And, never, ever, create empty folders ... it seems like a no-brainer but it happens a lot more frequently then you might think with people using them to force a specific heirarchy on their site or for the sake of stuffing keywords into their URLs or just because they think the final URL looks 'nicer' that way.
Last thought on why flat is normally better, homepages are likely to accumulate more links than any other page on your site and often more links than the rest of the site combined. So the closer an interior page is to the homepage the more benefit it will derive from the inbound links pointing to the homepage.
I like nested folders for a couple of reasons, some of which are:
- Clarity. A good structure will instantly signal what the page will be about, before a user or searchbot follows that link.
- Bolded keywords in URL in the SERPS.
- Using pages to flow juice to categories.
- Benefit of targetted anchor text, when using the URL for anchor text.
Compare: big-ecommerce-site.com/yoga-pilatus/accessories/yoga-mat/
vs.
big-ecommerce-site.com/yoga-mat/
And search queries like: "pilatus mat" or "yoga accessories". Which will work better for these queries?
- Structure. Your URL's will reflect in your breadcrumbs, allowing users to navigate your site through URLs (By removing a folder and going to a higher level in the site).
- Silo's. After the Panda update, and this is speculation on my part, Google might lower the imporance of "parts" of your website. Let's say only your blog is of very low quality. Google could discount /blog/ when you have nested folders. With a flat structure your removed "parts" or higher level categories from your site, and don't allow for this.
Ofcourse there are benefits to going flat too. But nested folder trees are not neccessarily a bad thing.