None of those have interfaces on par with say amazon or ebay or even facebook. ALthough i know facebook uses mostly ajax anyway. IN fact justin.tv and scribd really are just a cms that pushes the video rather then the site being based around the interface as it is with facebook.
Its not really that important just something that ive noticed. THen again there arent really any java sites that i can think of that are high load sites that have complex interfaces either. Meaning newer sites. MAybe they just arent in fashion anymore. Or everybody is just moving to ajax front ends.