Idea from http://mathematica.stackexchange.com/questions/18375/world-plot-without-borders-between-countries:

Graphics`Mesh`MeshInit[];
(* Can also use "Polygon", "FullPolygon" below *)
world=CountryData[#,"SchematicPolygon"]&/@CountryData["Continents"]//Flatten;
world = world /. GeoPosition[l_List] :> l;
ds=PolygonCombine@world;
Graphics[{Gray,ds}/.Polygon->Line]

ds

Count[ds, {_Real,_Real}, 3]