Great points. I've thought about some of these.

Currently, Firefox's bookmarks is the main task where I use tags these days. Bookmarks so quickly become quite a mess! I really like tags for the ability to have both a mess, quickly add things without having to think too hard, and ultimately being able to find stuff of course.

I had a quick excursion using Chromium for a few weeks--does it even have tags in the bookmark db? They weren't picked up when I exported from Firefox. I went back to Firefox because Chromium's address bar doesn't quite search my bookmarks and history the way Firefox does and only displays the top five results or so. Not something I can depend on to be able to find something back.

I really want to get back to having a load of tags on my music collection. Used to have that in Amarok, but I lost the DB many years ago. So useful, for custom playlists, weird personal microgenres that make sense only to you, tagging tracks you almost certainly don't want to hear if you put some album into a larger playlist (Daft Punk - Touch :-P) etc.

Anyway. Your thoughts:

1. Yes. For that, I imagine a powerful and snappy interface to organize tagged stuff. A bit like those automated MP3 ID3v2 tagger tools, but a bit more general. Should allow for mass re-tagging operations like: add tag #newthing to all objects tagged #onething + #otherthing but not #notthisthing. With the title matching "* about things". Only for objects (created) older than 1 year (because my mental schema also changed the way I used the #otherthing tag).

That's only power-users I'm afraid. I have no idea how to solve this for regular users. Although I've seen motivated/determined "regular" users structuring years of digital photos with folder systems in ways that maybe they wouldn't shy from such a tool as long as it's intuitive to use.

2. This is a big shortcoming of Firefox's tagged bookmarks. Back when I used del.icio.us (also many years ago), there was a bookmarklet I could use to add a site to my del.icio.us bookmarks. The greatest thing about it was that it would predict/suggest tags for your bookmarks, I miss this so much. It did so in two visually distinct ways: First, predictions on your own bookmarks, afaik it was just a set of tags that you commonly used in conjunction with the one or two tags you've typed so far. Maybe it also matched keywords in the title and url. If I were to implement this I'd sort them by Bayesian P(#newtag|title-url-keywords-tags-typed-so-far). The second set of tags were suggestions based on what other del.icio.us users had tagged that url (less useful and less privacy).

3. I think you could have both? But most importantly, what helps me a lot to navigate and orient myself in this tagged mind-palace (nice analogy btw), is the ability to not just sort and slice your database by tags and combinations of tags, but to also just be able to browse everything sorted by time. I find this in the photo gallery on my phone, which is an utter mess, but if I really need to find something, I switch to by-date view (groups by month). Even if I don't exactly recall what month a photo was taken (or it could be a picture that I saved from Twitter, or maybe that someone sent me by IM), scrolling through I see pictures through time and usually I quickly get a familiar feeling "wait it was before then, and after ... yea .. when the thing .. ah! got it!".

It depends on how your memory works of course. But I imagine it would work because even though you can tag and re-tag and restructure your documents, the ordered slice of time-line of say 1.5yr ago hardly changes if at all.

4. Yes exactly. You might notice the "solutions" or ideas in the points above are all based in some way or another in this observation.