The problem is, only advanced users would know to leverage their tags for nested organization. I have used Evernote for two years, and I have never used the Tags feature. "Tags" so broadly apply to different functionality in different applications and websites, that it is not an inherent given, for new Evernote users, how they should utilize their tags to their advantage. From a UX perspective, it makes sense that a user would think Evernote would have folders. Here we have an application that allows you to collect and create lots of individual pieces of content. Yes, it could be managed with a tagging system, but I'd argue that a new user would expect "Folders" to organize their content before "Tags." My feeling is that Evernote wants people to get to know their usability style. They've created and defined a system using Tags, and people should learn how to use Tags. But there is value from a UX perspective in providing the features that users expect, rather than teaching them how to use your software. Build software that users already know how to use. As a use case, I searched for and found this thread because I was confused why you could drag and drop Notebooks onto Notebooks to create Stacks, but not Stacks onto Stacks to create sub-Stacks. I was so sure (and excited) that I'd be able to do this, and then was surprised when I wasn't able to. Why not make Stacks stackable? What confusion or disadvantage would it generate? Does it encroach on the functionality of the Tags system? I'd argue that it enhances it; I can't see any downsides to enabling this functionality. Have any usability surveys shown that users don't want or expect folders? Not only that, but it would be wonderful to be able to share sub-Stacks. I love how in Dropbox or Google Drive (also repositories of content), I can create my own hierarchy of folders, and then share sub-folders. I would love to be able to have a "Clients" Stack, and then all of my clients' Stacks inside it. And then maybe Stacks inside those Stacks, to share with different departments in the company (Accounting, Sales, Marketing, etc).