To mock something fast and loose with geo-json data for the world, this is your fix. Legal status of this dataset: dubious?
For a good time, drag them to http://bl.ocks.org/1431429 and paint the globe!
[A] convenient mechanism for generating TopoJSON files from Natural Earth.
Natural Earth is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data, with Natural Earth you can make a variety of visually pleasing, well-crafted maps with cartography or GIS software.
Natural Earth solves a problem: finding suitable data for making small-scale maps. In a time when the web is awash in geospatial data, cartographers are forced to waste time sifting through confusing tangles of poorly attributed data to make clean, legible maps. Because your time is valuable, Natural Earth data comes ready-to-use.