[danabramov]

Weird there's no number for Russia on the map. I thought SO scores a lot of Russian visitors (many of whom satisfy those two criteria).

[kozhevnikov]

According to [1] and [2] Russian is still behind some other languages, i.e. Hindi, German and French. Seems that number of visitors is just one of the signals taken into account and not the main one.

[1] http://www.alexa.com/siteinfo/stackoverflow.com

[2] https://www.quantcast.com/stackoverflow.com

[ufo]

The map was just for Portuguese-speaking countries.

[danabramov]

Ah, that explains it! Thanks.