As the web becomes more "2.0" we're collapsing collections of pages into fewer and even single, more dynamic pages. Instead of ten pages of event listings, we might have page that loads further items dynamically as you scroll. The state that was once static to a page is now loose and can alter in the lifetime of a page, which grows longer every day. Parameters of the page state have always sat in either the path, in URLs like http://myblog.us/post/how-are-you or the querystring in cases like http://www.coolstore.com/view.html?product=4356 . Neither approach works when those parameters are changing for the life of the page, and where a single URL needs to be able to represent these multiple parameter values at any time. In most uses so far, the bullet is simply bitten. The user can browse to your site and click around, and if they bookmark or send the link to a friend, they'll always come back to the front page, because the state of the page is no longer held in that ...