I'm a big fan of tags, and I would argue that we are giving up the folder metaphor, it is just happening online first (tags was a big part of "web 2.0" sites, gmail's labels, using google to find files based on keywords, etc).

The location where files are stored is where tags are a bit awkward. The folders are clear there. It's easy with folders to copy a picture from an SD card to my hard drive. From hd to a network mount.

The alternative would be to have magical tags, so everything you gave the 'hd' tag to, it would be stored on your hd.

In fact, the whole concept of adding a storage device to the system is strange with tags. Mount a 1Tb network share and automatic indexing starts? A standardized format for storing tag-information? What about computers that just change files directly without updating the tags? What about incompatible formats?

I wonder if applications could do a better job at tagging up files they create compared to the approach (in apple spotlight) to have search engine plugins that can find tags based on file content (mp3 id data, jpeg exif data,...).

If applications were more tag-aware, they could at least allow you to browse your files by tags instead of by folders.