In the long term, SPA features are absolutely necessary, especially when it comes to HTML5 apps (also in regard to Windows 8 WinRT or upshot.js - a key part of the forthcoming Microsoft RIA stack). A good SPA addresses the following issues: - real permalinks - page titles - a working back button that fully degrades - different data states like http://bit.ly/zpybmz - client side caching - asynchronous updates/communication - ...what else? (please add if I missed something) Example SPA: http://pjax.heroku.com/