I wasn't referring to intranet vs. internet apps, but rather apps that generate public content that can be viewed without authentication (e.g. Twitter) vs. apps

I wasn't referring to intranet vs. internet apps, but rather apps that generate public content that can be viewed without authentication (e.g. Twitter) vs. apps whose information is entirely restricted to authenticated users (e.g. GMail). Basically: does the app generate stuff that needs to be crawled by a search engine? While client-side routing and state preservation used to be a very difficult thing, these days it's actually pretty straightforward (ngRoute, Backbone router, Ember router, etc).