I recently brought my wiki back to life at wiki.datguy.net datguy.net/wiki, consolidating my old wikis onto a newly upgraded MediaWiki installation. After I went through and removed a lot of dead links, I decided it was time to work on the configuration. The first thing that had to go was the default URL structure (i.e. http://wiki.datguy.net/index.php?title=Main_Page). I was hoping to simplify it to http://wiki.datguy.net/Main_Page.
I found a page at mediawiki.org describing how to shorten the URL, but it recommended against page names in the root directory, with a link to a warning page. As much as I want to have pages directly in the root, I didn’t want to deal with the complications yet – so I picked a random letter to use as a virtual directory, resulting in http://wiki.datguy.net/w/Main_Page.
EDIT
That extra virtual directory kept bugging me, so I moved the MediaWiki installation out of wiki.datguy.net into a directory underneath datguy.net, where I could use the /wiki path. I changed the old domain to redirect to the new location — http://wiki.datguy.net/Main_Page redirects to http://datguy.net/wiki/Main_Page. However, the wiki subdomain still has the problem that they recommend against — http://wiki.datguy.net/robots.txt is redirected as if it is a regular page, and displays an error when http://datguy.net/wiki/Robots.txt is not found.