A subtle advantage of simple wikis
One of the interesting things about programming DWiki is how it's wound up making me notice and appreciate the subtle cleverness of Ward Cunningham's original simple wiki design, in particular the choice of a flat page namespace. Many of the advantages are relatively technical but there are more abstract ones, one of which I stumbled into today:
You do not have to taxonomize information before you put it into a flat wiki; you just have to give it a reasonably good name.
When you have a page hierarchy of some sort, you have to worry about just where something new goes. And because cool URLs are permanent, you really want to think about it before you create the page, so you can put it in the right URL. In the extreme case you may have to create an entire hierarchy before you make one new page.
A flat page namespace doesn't have this issue; you just make up a decent name and go. You can layer taxonomies on top of it, but they're necessarily more fluid; more tags than hierarchies. And that means they can be added afterward, so you don't have to worry about them up front. Less worrying and planning, more actual writing.
(I still don't regret using a directory hierarchy in DWiki; it makes sense for what I want. But I can definitely appreciate the shade of the grass on the other side of the fence.)