I know this topic is likely to become subjective, therefore it is not about my particular web application I am working on.
For JavaScript, I haven't worked with MVC libraries like Backbone.js but I see the advantage in decoupling logic and views. On the other hand, it may just not be worth the time to learn the framework and adapt the application to make use of it. Moreover, handling all views in JavaScript makes SEO much harder, I guess.
So how should I decide whether it makes sense to use Backbone.js or a similar framework given the concept of a web application? On what depends the decision?
Any help to make the question more objective is welcome.