Years ago, we would make a GeoIP lookup using a script tag added to the skin by CentralNotice. This was necessary to correctly geotarget campaigns to users, without splitting cache, etc.
Let's decouple GeoIP from CentralNotice. It could go into MediaWiki core or better yet, its own library and subsystem. Not sure what the best form would be.
Everything which depends on the Geo variable should have an explicit dependency to this library.
We should audit the privacy implications of all geodata usages.
The last I checked, the following extensions make use of GeoIP:
The following extensions seem to be performing their own geolocation: