1. A method performed by one or more computer systems coupled to a packet-based network via wired or wireless connections to obtain geographical location information for Internet Protocol (IP) addresses, the method comprising: receiving a first plurality of advertisement (ad) requests from the packet-based network, each respective ad request among the first plurality of ad requests including location components of an associated mobile device, the location components including one or more of an IP address, a set of geographic coordinates, a name for a geographical region, and a code for a geographical region; selecting a second plurality of ad requests from the first plurality of ad requests, each ad request of the second plurality of ad requests including a first IP address and having a set of geographic coordinates that meet a first set of predefined criteria; deriving geographical location information associated with the first IP address using geographic coordinates in the second plurality of ad requests; and storing the geographical location information associated with the first IP address in an IP region database accessible by the one or more computer systems.
2. The method of claim 1 , wherein at least one of the one or more computer systems has access to a database storing therein a plurality of static centroids, each respective static centroid of the plurality of static centroids being a fixed location in a respective geographic region selected from the group consisting of: a city, a town, a county, a state, a country, a region associated with a postal code, and a region associated with an area code, and wherein selecting the second plurality of ad requests comprises: determining that each ad request in the second plurality of ad requests has a set of geographic coordinates that do not correspond to any of the plurality of static centroids.