www and non-www

Was following this thread:

https://premium.wpmudev.org/forums/topic/sitemap-not-found-by-google-webmaster-tools

Would be interesting to have a good article on WPMU.ORG about the www and non-www usage. When I was having problems once it's pretty hard to search using the terms www and non-www.

Unless someone has another good article on it and tips on how it relates and interacts with Wordpress/Google etc?

Anyone else interested?