It's really cool. Care to explain why do you have http://mbostock.github.com/d3/d3.v2.min.js in header that has only one line - links to actual d3 at http://d3js.org/d3.v2.min.js? Am I missing some reasoning behind this? It doesn't seem very reasonable. Adds two unnecesary hops to two different domains? If you dont want to host d3 why not just reference it directly in header from d3js.org?

Edit: Oh, and how you distort svg to make it look spherical while dragging? This is very cool.