[theamk]

I think most of the photo organizers offer this? I remember using digiKam back around 2006 or so, and it already had this feature.

I think tags have limited scope. They are great for photos. They are OK for music, but strictly in addition to the main hierarchy. You could use them for text docs, but folders + full text search is much better. And file level tags are completely useless for code/programming

[maxerickson]

If you have a rich set of tags, you can have more than one main hierarchy.

Artist sort, year sort, genre sort, etc. Genre is really hard though.

There isn't much reason to use tags as the only way of organizing things though, they work great as views.

[theamk]

Agree, views, but not main organizing principle.

For example, my music collection is big and diverse, and both "year sort" and "album sort" are kinda useless now, because there are actually multiple disjoint subsets. There is no point ever in showing me audiobooks for year 2010 and regular music for year 2010. I always only want a subset of it.

This is what I meant "strictly in addition to main hierarchy" -- let me keep my folders, and maybe when I want to go deep enough, I want to browse by tag. But even then it would not be a hashtag-like tags that the original page refers to.