I can think of few things less exciting, and less useful, than tagging. In the example Apple gives, the user clicks on a tag in the sidebar and all the files with that tag appear in the main area of the Finder window. If you have only a few dozen files, this may be just the thing for you, but I actually use my computer, and this is absurdly inadequate and the reason I’ve never cared for tagging. If you restrict yourself to a small number of broadly applicable tags, each tag is likely to apply to hundreds of files. If you use more specific tags, the number of tags explodes and they become impossible to remember. Either way, the tags don’t help you find your files.
Some of the points that folks are making regarding tagging are reasons why they themselves do not use tagging. Some are illogical arguments that tagging systems fail if you don't tag every file or some other variation. I find that nested folders are the same way for me in that I mis-file something and can't find it. Yadda, yadda, yadda skip ahead to ever popular there is no perfect system argument.
It goes back to a simple need to develop your filing system to use the tools that work for you. Tags can be part of this system and will continue to be part of my system.
I don't have a perfect tagging system nor a perfect folder system. I rely on a mix of Together (previously Yojimbo), nested folders, and Tags to try and find my files. To date this year, I have chosen to file over 2000 files. Too many I am sure. However, when prepping for a review or meeting, I find myself digging for some random file a lot. Of course not every one I filed and often not the files I thought I would search for. So I will continue to use tags and folders and whatever else I can to find these files when I need them. I view it this way, I am more likely to find a file I tag and put into a nested folder in Together 3. I outline a couple of ways tags will be great for me in this post. Namely that I tend to remember files by a number of ways including who sent the file to me and about when. I could imagine that geo-tagging files could work for some folks. Think something like I started that file at the office or coffee shop or in The Chemistry Bldg. or whatever. The main point is that however you tend to think about files, there are some good auto tag ideas to build a great filing system.
For all of you corporate types I offer one simple tag idea: fromYourBossesName. I think you know what I'm talking about. Run with it and please share tips to me. The auto tagging script from email is a great first step. I am also looking forward to seeing how Trickster and others help me quickly find and parse my files on a daily basis.
We will see a lot of creative stuff coming from folks as they begin to use tags now that they will be system wide. Ditto for when creative Devs get behind this. I'm up for beta testing...firstname.lastname@example.org.