Depending on the other content of the page and the nature of your traffic/user data, it might make more sense to take advantage of caching by making the initial loaded resource (the HTML file) completely static and loading the bootstrapped data in a single separate request.
Yes, absolutely. If the initial HTML page is heavy, and can be cached for all users, then separate makes sense. If the initial HTML page is light, or user-specific (the usual case for a backbone app) then bootstrapping in a single HTTP request makes sense.
