I've been working on a file organization system that incorporates tags, and I must say I agree with the GP. Tags improve display and search over hierarchies, but they require no less discipline on the part of the user. Without some way to automatically mass-assign meaningful tags to items, which is an insanely difficult problem in the general case, the user is forced to manually tag every single item they add to the system. AI could help do this, but not much. First, consider that mistagging an item can make it practically impossible to find again. Second, consider that semantic tagging can be almost arbitrarily abstract; imagine tagging a text document with "cyberpunk" or an image file with "parody".