User 'folders' for uploaded files?

Is there any best practice / tutorial for organizing user uploaded files?

In my app I have an 'uploadable' polymorphic structure where the user can upload files to pretty much any model etc.

Currently the structure is flat - all files ar dumped into a bucket per associated record. My users are going to want to organize these in a normal MacOS Finder / Windows Explorer file structure.

My thought is to add a nested 'folder' structure DB table (with the ansectry gem). It belongs_to the uploadable record and then each upload belongs_to a folder. If there is no folder it's just a root file or a have a default root folder for consistancy.

Does this seem reasonable? Am I missing anyting here?