rlange - 2:33 pm on Jul 27, 2011 (gmt 0)
Google Analytics has a specific option for tracking subdomains when generate your tracking code.
For some reason, though, the different GA interfaces give you different tracking code. When you select "One domain with multiple subdomains", the current version adds a single line...
...whereas the new version adds two lines...
I'm not sure which one is preferred.
Edit: Pff... The "Modify the tracking code" link on the page chrism linked to above blends the two into a third option; the two lines from the new interface, but with the dot-prefixed domain name of the current interface.
Google, Google, Google...