That may not be true for very much longer.
As August ended, Google dropped this little bomb casually:
Most people think of example.com and www.example.com as the same site these days, so we’re changing it such that now, if you add either example.com or www.example.com as a site, links from both the www and non-www versions of the domain will be categorized as internal links. We’ve also extended this idea to include other subdomains, since many people who own a domain also own its subdomains—so links from cats.example.com or pets.example.com will also be categorized as internal links for www.example.com.
This is, I think, a good thing. They make sure you understand that ipstenu.wordpress.com won’t be the same as jane.wordpress.com, which makes sense since their own blogger platform runs off subdomains as well. Somewhere in their logic they know ‘Aha! Ipstenu doesn’t own wordpress.com! But she does own Ipstenu.org.’
To reiterate, this only affects things in Google’s Webmaster tools:
This update only changes how links are displayed in Webmaster Tools. It doesn’t affect how links are valued in relation to the search algorithm or ranking. It has nothing to do with Panda, nothing to do with keywords, nothing to do with PageRank.
I fully expect that it’s going to change and expand. Since most of us end up registering our ‘master’ domain (i.e. ipstenu.org) off Google Webmaster, they can easily leverage the data they already have in order to tweak search engine results. Another tactic would be to start using a new meta type tags. After all, the big guys already organized schema.org (which isn’t as picked up as it might be yet).
Sidebar: Schema.org’s problem is how complicated it is to fold into CMS tools. If they’d started by releasing this with a couple plugins/extensions for the popular open source tools like Drupal, Joomla, MediaWiki, MovableType and WordPress, which as they’re open source, they could have, we’d be way ahead of the game. As it stands, the one WordPress plugin I’ve seen requires you to import SQL tables! If they get schema ironed out so it’s simple and easy to use, then we can add in ‘parent’ or ‘main’ site parameters to our code and every search engine can know ‘halfelf.org is internal to ipstenu.org, but taffys.ipstenu.org is not.’ And wouldn’t that be cool!
Personally, I have ipstenu.org, ipstenu.org, halfelf.org and so on all listed separately in Google Webmaster right now. I could do that with subfolders as well, to track data internally to itself (i.e. each subdomain/subfolder), and still track them at the master level with the main domain.
So no effect on your SEO or ranking or any of that stuff, but a nice change for Webmaster Tools.
Where do you see this going?