Hi Jan,

mainly this should be due to system adopted for users geolocation, that is not based on IP address.
Geolocation based on IP address is too much inaccurate due to proxy, filtering, routing, hosting mask, etc

So the solution adopted to locate users is based on user agents HTTP headers. Of course also using this solution can be situations where browsers send spoof headers, so looking as belonging to a country also if located in somewhere else.

Having no data at all about geolocation could means that stats are referred to bots that are almost anonymous. If the Ip addresses belong to specific ranges they can be filtered out to avoid stats recording.

John