Flickr, del.icio.us, and Technorati tags.  GMail labels.  WordPress categories.  I think the future of operating systems and file storage is with this method, hereby known as TLC (tags/labels/categories).  The major advantage of this method of organization is that a user doesn't need to store a file is just one folder.  Many different labels can apply to a single file.  For example, let's say I have some financial information stored in some Excel files.  Instead of organizing my files like this:  c:\Documents\Personal\Finance\ and c:\Documents\Work\Finance\, I can just assign tags to the files such as personal, work, finance, excel, etc.  Now when I'm looking for my financial files, I can opt to show all files with the "finance" tag.  This would show all my financial files, both personal and work-related.  Or maybe I want to keep personal and work separate, so I only show files with the tags "finance" and "personal". 

My prediction is that the next major advance in operating systems and/or file storage will be with this.  And I have a feeling Google will come up with it.