Here's a question I have come up against a few times.... Scenario - Have a WP blog with a decent level of unique content, reviews etc, aged domain, ranks for name, some related terms and plenty of long-tail... If I then want to spoil it all with a feed driven affiliate "shop" - using xml feeds so no chance of unique content, thousands of pages so potentially a killer for the SEO. Where would you put it ? I'm thinking sub-domain so as to keep the two separate, and not spoil the existing profile the aged site has... Of course this doesn't give the sub-domain site pages as much chance of ranking as if it was on a sub-folder but in these post Panda days maybe it wouldn't anyway.