if you haven't been paying attention Google's panda update is destroying content based websites. If you've been hit or are planning on running a content based website (text content) then you should seriously look into using subdomains for either Authors (UGC websites) or categories (moderated sites like a blog or news). http://blogs.wsj.com/digits/2011/07/13/site-claims-to-loosen-google-“death-grip”/ http://insights.chitika.com/uploads/Google-Update-Places-Emphasis-on-Domain-and-Subdomain.pdf
I don't give into this. This is irrelevant... Totally. Content based sites would by anything. sub domains are recognized by google just like they were last year. No change really.
yeah because google never changes... but the point is that Panda is a domain wide penalty and is likely not going anywhere any time soon. using subdomains can help you keep content from penalizing your entire website.