What's wrong with using UN's geoscheme http://en.wikipedia.org/wiki/File:United_Nations_geographica... instead of inventing your own categories?
The poll is basically a US centric poll with the rest of the world thrown in as an afterthought, unfortunately that's a pretty accurate representation of the way many tech people see the world.
This actually causes a feedback mechanism that now means that being located 'in the valley' translates in to a very real competitive edge.
> unfortunately that's a pretty accurate representation of the way many tech people see the world.
True that.
Europe is traditionally divided from Asia at the Ural Mountains: http://en.wikipedia.org/wiki/Europe