Luckily, Zane Kolnik stepped in to demo networked Wordpress and domain mapping. To start, Zane offered-up the Wordpress codex for creating a network--simply visit http://codex.wordpress.org/Create_A_Network to get the full breakdown and requirements.
In essence, you will simply be placing code in your wp.config.php file and your htaccess file. After doing so, you will be prompted to login--if you are unable to login you will need to remove the code and start over (bummer).
In the next phase, you will need to choose whether your networked site will use subdomains or sub-directories--choose wisely as you will not be able to change your mind! To help you with your decision, below are two website examples. Visit each and compare the urls--also check out the content organization and notice how themes are adjusted according to the subdomain or subdirectory.
(see "Our Sites" menu)
(Click on Main Nav categories)
*In version 3.1 you will see the "network admin" as a top right menu option.
*Be sure to enable uploads for the multisite in your network admin settings--towards the bottom there will be check boxes for images, video, and music.
*Initially, your uploads per site are limited in both number and in size. For example, each site may be only allowed 10 images at 1500kb each.
So why would you use this feature?
*Easily delegate administration
*Control user permissions
*Use separate themes / build unique themes within one website
*Works great for theme developers
*From a production standpoint, the subdirectory option helps to organize robust content
One attendee stated that this would give her a level of control that she required for a franchise business that will need theme and permission customization for their different regional locations.
To finish it off, here is Zane's favorite domain mapping plugin and his go-to tutorial
I am more of a student then a teacher, so I would encourage you to review the Worpress codex and visit blogs like Zane's for more information!