Wouldn't it be nice if you could organize your computer files around topics? The old method is placing all your files into a single folder; but tags allow users to sort files into multiple folders at once. This could be a perfect addition to Web OS (a.k.a. cloud-based operating systems) -- social media already does this -- it seems natural to sort computer files around topics.
For each hash-tag it could generate a folder.
It appears that Apple is going to run the first successful cloud-based operating system with iCloud. Google Drive might also evolve into a cloud-based operating system, or maybe Chrome will be ported.