We use the Google Web Toolkit to defer loading large pieces of data that compose slots around the page. The result, which you could achieve with any asynchronous mechanism, is that the page is up fast, and then details pop in as they're ready. If we waited to retrieve all of the data and render the HTML on our server, pages that currently start presenting on the browser in one second or less would take 4 or more seconds. Basically, if it's below the fold for most of our users, we defer loading it.