This is what I wrote three years ago about The Brain, one of the tools I was using heavily as a personal information manager:
I've decided that I need tools that have a bit more of an old-fashioned linear structure to them after dealing with wildly associative stuff like The Brain for a while. When it comes time to put down a few simple thoughts in order and prioritize them by when they need to get done, The Brain is just not doing it for me. In addition I have literally thousands of "thoughts" cluttering my main Brain database, and they remind me not of what is happening now but of what was happening them. I've moved on; it hasn't. More's the pity.from Vacuum #64, on the 2001 Ann Arbor Fourth of July parade.
Since then I've taken up wiki whole-heartedly (see Socialtext for more detail on that) but find myself gravitating back to The Brain every once in a while when I found myself offline and not able to get to the net. In the process I discovered something I'm still coming to grips with.
There's something very liberating about taking a blank slate (like an empty Brain) and filling it up with a bunch of brand new content. I counted as I went and found that I could key in 150 ideas (mostly a word or phrase, some rarely with a paragraph or two) in an hour and a half. This all in a completely new workspace, devoid of previous associations, and where I am perfectly happy duplicating something I've already written about or linked to or made a note on before.
As it turns out I've now done half a dozen 150 node Brains at various Pittsburgh area coffee shops, airport lounges, and other places where wifi is too dear; I'm getting pretty good at the form. I always stop at 150, because beyond that you get tempted to grow to infinity, and The Brain doesn't work at infinity. I keep a page for "People", for "Books", for "Idea flow" to capture the good ideas, and try to keep the top page neat and limited to a dozen top level categories nested no more than two or three deep.
This is what I'd call (and what Lou Rosenfeld would call) disposable information architecture, building a structure to capture a few ideas very quickly and then letting them dissipate once you are done. In my mind you have it for an audience of one as ideas are forming. A good disposable IA is very forgiving of errors since after all you're going to get rid of it as a day to day working tool.
I haven't quite figured out how to dump quite so many ideas and associations into a wiki quite so quickly - if you did it you wouldn't end up with 150 different pages because the wiki style expects paragraphs, not individual words. I'll have to try once I get my (offline) laptop wiki running. It may be that the architecture is actually pretty reusable, even if the contents are deliberately constrained to what comes out in a single 90 minute offline session.