BigPipe has been around for a while in Facebook. I love how the pagelets load all at once so that the first one to get loaded comes first. Also the idea of prolonging the javascript until all page content is loaded it a great idea.
Here is the page about BigPipe:
http://www.facebook.com/notes/facebook-engineering/bigpipe-pipelining-web-pages-for-high-performance/389414033919
I love this idea and may implement it on a site next time I am building a multimedia site. The nice thing is the main parts of the site are loaded very fast and then the rest are loaded with AJAX.
