@ETpro – it’s a little bit different situation…
the links @LostInParadise gave in the question show the exact same content regardless of the subdomain used… you could use anything for the subdomain portion and it will always show the same, so it’s not a question of the best way to divide the content
For example, if a spider follows the incoming links from this post it will index each as a separate page and rather than all the “juice” going to mathed.org, you’re going to see that split between the various subdomains used as examples.
The same happens when half your links would come in to a www.domain.com and half would come to just domain.com. Because we can’t control how people show the link, we have to do something about where that link points, and htaccess takes care of that in a way that spiders can follow to realize it’s all the same content/page in reality.
He can do the same here, not lose any incoming links (or people/traffic) and move on to math fame and math fortune.
The link to Matt Cutts shows that subdomains don’t receive any benefit (or penalty) over directories as a way to separate content.