It looks like Apple is finally going to start making serious changes to the way we interact with the file system. Which is to say, they already have in the case of music and photos, where you have subsets and filters of a "library", as opposed to folders. But now it sounds like they're taking it to the next level.
Strangely enough, I wrote about this kind of file system back in 1997, and I occasionally get email from people who are implementing the ideas. I started writing a much-updated account of what the "Liquid File System" might loook like a little while ago, but got distracted by something or other. The angle for the new article was going to be that OS interface design has stagnated, and that slapping a web interface on the file system didn't really help anything.
Anyway, what I imagined in the new, faster processor reality, was an interface where a number of preset filters could be applied to a "library" of information - emails, files, photos, etc. along with their associated metadata.
So you'd have a one-window interface with a the full library in one column, and various filters in the left column. These could be things like "updated in the last 2 days", "name contains '[a keyword]'", files type, and so on. So I could click on the first filter and immediately limit the view to files updated in the last few days. Then I could click on the "images" filter to show only the images that had been updated in the last few days, and if I still didn't have what I wanted, I could filter by the contents of the name, which OS X already does.
The point is, even with just the most basic metadata that is already available in the file system... and it's a very powerful way to deal with data.
It gets better when you add functions like Apple is apparently adding, like creating relationships between files (I remember talking to Hans Speijer about this back in 1998--he had a lot of similar ideas, but was specifically into connecting files to each other--when I tried to convince Be to use something like the Liquid File System in their OS... but they didn't seem keen on taking strategic advice from a 17 year-old non-programmer for some reason).
Another possibility would be for the OS to notice which files you use in the same session, and create a fuzzy list of related files in a third column, which could be promoted to 'related file' status, or dropped off the list.
Also, rather than having folders, setting up categories in the left column as filters would be interesting (and along the lines of the original LFS proposal). Clicking on the category would constrain the current view to members of that category, but dragging a file or files onto the category would add that category to their metadata.
Obviously, custom search constraints could be created based on what was most useful. The technology is actually already there. OS X is supposed to do this (though I just tried it and got an error), though you can't combine them.
I'm mostly happy that I'll get to use this system sometime in the near future, instead of just talking about it. (I had a similar experience when voodoopad came out, it being similar to another 1998 idea, notespace.)