This, entirely. You can effectively construct your own framework by combining other pre-established routers, models, and views (plus whatever other modules you might want). You still get many of the benefits of using frameworks (testing, docs), but it's much more flexible and has the potential to be leaner. You still need to establish best practices and a relatively consistent application design, but these are things you'd want to do anyway... even if using Backbone, or whatevs.