[manulp]

Maxmind offers free databases to do IP localization : http://dev.maxmind.com/geoip/legacy/downloadable/

It's not extremely precise, but is enough for applications like this. Notice for instance the point up north in Canada, a lot of IPs will be placed there. It's in the middle of Manitoba, and there's pretty much nothing there. I believe it's the geographical center of Canada, and the default value when no other coordinates are known.

[mpetrov]

That's pretty much exactly what's happening with some locations. We do our best to get an accurate location based on a few sources, but ultimately Maxmind is the database we fall back to for pure IP based location if that's all we have.

[ntaylor]

We have the same difficulties with our Maxmind IP database. An inordinate number of our users supposedly live in Potwin, KS, AKA the geographical center of the United States.