This would make it very easy for users to select the root of a program and see all files related to it under descriptive tags, or select a tag and see all of the root tags with files that use that tag.
Why not? Sounds like it would make a good alternate file system. (And for those of you who are already crying about losing compatibility with existing systems, just have it default to to /root-tag/optional-tag/optional-tag/file)
I personally like Macintosh's ability to make programs look like one file/folder that gets executed in the system, and if you want to delete the program just delete the one file and you're done. None of this spraying itself all over the system. But I wouldn't trade anything for Macintosh's 'fancy' graphics or overpriced computers. No thanks. I just think we could learn a few things from them.