I'd disagree that it's never going to be worth doing something of that scale. Protovis/D3/Raphael visualizations could easily get to that level of complexity. I

I'd disagree that it's never going to be worth doing something of that scale. Protovis/D3/Raphael visualizations could easily get to that level of complexity. I've already used Protovis to display 2mb geojson files, so I think people will use all the SVG performance they can get.