What I learnt from Quora is the importance of footprint. The size of your site doesn't matter; what matters is uniqueness of content. So Quora uses canonical links to group questions it deems similar into 1 single "seo" bundle. Quoras difficulty was in group questions. At the elioWay we will ask users for a short, CamelCased name for their app - forcing users to create very "keyword" focused name to weed out "seo" weakness middleware. Maybe.
