SpamikazeWiki:

Structure in the wiki

Hierarchy levels

Many conventional websites use very branched structures with many hierarchy levels.

In wikis linking is heavily used. A simpler structure is often used to simplify matters:

Conventions

A wiki gives much freedom to the users; there aren't input masks like in database applications, but you can, in principle, do whatever you want and do it however you want.

Of course, you should avoid that to prevent complete chaos. B-)

That's why it's usual for new wikis to think about structures and conventions, such as the:

It's usual for older wikis to simply carry on using existing structures.