walkman - 6:17 am on Jul 15, 2011 (gmt 0)
Think of the nightmare for G if a single bad subdomain tanked the entire wordpress.com site. So they must have something built into the algo determining the relationship between subdomains and domains - and they probably use interlinking to determine the relationship - and look how they are treating their own blogspot structure - the subdomains link back once to the domain within an iframe in the nav bar at the top, and the domain does not any pass link juice to the subdomains. That's no relationship at all!
Your explanation makes sense but I guess we'll soon see if G added it or not. It depends if Panda really want to screw cross-linking 'domains' as part of the cluster.
Leaving Hubpages aside this can very easily screw innocent sites. Each folder /subdomain can have a different section or pages with a different purpose and here comes some 'Panda' that crushes you. And not even a private email with suggestions from Matt Cutts. A few days ago I no-indexed my most visited page, that one probably has even has more links than my home but it's different. You visit it, look around and leave. I am seeing if it skewed my site or not. So much for focus on the content /user, huh :) ?
Footnote: Edmondson from Hubpages wrote a scathing editorial on Google how they are promoting Youtube and Blogspot while penalizing /Pandalizing others, er competitors. Specifically mentioned how many junk vids youtube had, how the moved up etc. Not to revisit it but many of us have noticed Blogspot junk go on top lately. I wondered about Matt's advice and especially the "among other things" part. I'd like to know too, I got a family to feed as well.