I've been searching for a answer to this since before the Panda update (namely, how are subdomains viewed by Google's algo). 3 years ago, I heard talk that subdomains were treated as separate websites, and as such one would conduct SEO as if they were separate. With more and more big players using subdomains, it seems as if they can be implemented without being seen as separate sites. In a post-Panda world, do sub-domains reflect on the overall quality score of a site? Or do they each receive their own quality score? I understand this may be difficult to determine with any certainty, but I'd be interested in hearing the experiences of others with regard to this issue. Thanks!
Great question! I was looking to build on to a new site and wondering whether it would be hit by one of my sites that was hit by Panda.
Background: I had some data to review on two of my other sites. Both were hit by Panda 1.0 (-40% and -65% Referrals). I found a lot of useless user generated content on both sites. When looked as a whole, they accounted for rough 50% of the total pages on those sites. I removed all those pages about 2 months ago and still no change. No Panda 2 or 3 changes since.
I have a subdomain that I use for premium content for each of those sites. There was 0% Google referral change post Panada on both of those sites. In fact the referral numbers for March and April are an exact replica of one year prior. 1 site sees 10,000 Google referrals a month. The other sees 7,900 G referrals monthly.
So in my case, subdomains were not affected at all by root domains that were Pandalized.