Oh when it comes to streaming files then I totally agree that the server should do the work. This is more about reducing the visible load time for dynamic pages on a site. My example points to my site (e.g. http://daysoutnearme.com/hubs/city/bath) which uses it to improve the load speed of a heavy processing page; the map loads instantly when the remaining chunks of the page come through as the JavaScript has already been processed by the browser.