5. A system, comprising: a computer data repository that maps specific IP addresses to specific behavioral segments, said mapping derived from behavioral data collected from each of a plurality of Internet Service Providers (ISP), said behavioral data including information collected by the ISPs regarding Internet access activities of their respective subscribers, said behavioral segments reflecting subscriber interests; and a server, comprising one or more computing devices, that provides network-based access to the computer data repository via an interface, said interface configured to receive a request that identifies an IP address, and to look up from the computer data repository, and return information identifying, one or more behavioral segments corresponding to the IP address, wherein the server is programmed to respond to said request according to a method that comprises: determining whether the IP address can be mapped to a subscriber-specific behavioral segment that is specific to, and based on Internet access activity of, an ISP subscriber associated with the IP address; when the IP address can be mapped to said subscriber-specific behavioral segment, returning, via the interface and in response to the request, an identifier of the subscriber-specific behavioral segment; and when the IP address cannot be mapped to a subscriber-specific behavioral segment, returning, via the interface and in response to the request, an identifier of a region-specific segment that reflects user preferences associated with a geographic region corresponding to the IP address.
5. A system, comprising: a computer data repository that maps specific IP addresses to specific behavioral segments, said mapping derived from behavioral data collected from each of a plurality of Internet Service Providers (ISP), said behavioral data including information collected by the ISPs regarding Internet access activities of their respective subscribers, said behavioral segments reflecting subscriber interests; and a server, comprising one or more computing devices, that provides network-based access to the computer data repository via an interface, said interface configured to receive a request that identifies an IP address, and to look up from the computer data repository, and return information identifying, one or more behavioral segments corresponding to the IP address, wherein the server is programmed to respond to said request according to a method that comprises: determining whether the IP address can be mapped to a subscriber-specific behavioral segment that is specific to, and based on Internet access activity of, an ISP subscriber associated with the IP address; when the IP address can be mapped to said subscriber-specific behavioral segment, returning, via the interface and in response to the request, an identifier of the subscriber-specific behavioral segment; and when the IP address cannot be mapped to a subscriber-specific behavioral segment, returning, via the interface and in response to the request, an identifier of a region-specific segment that reflects user preferences associated with a geographic region corresponding to the IP address. 6. The system of claim 5 , wherein the computer data repository further includes, and the interface provides access to, a mapping of geographic regions to behavioral segments, said mapping derived from aggregated behavioral data collected from a plurality of ISPs.