4. A computer-readable storage medium that stores instructions which, when executed by one or more processors, causes the one or more processors to perform particular steps comprising: determining if a top-level domain of a particular host is a regional top-level domain; and if the top-level domain of the particular host is not a regional top-level domain, then determining one or more regions associated with the host based on which other hosts contain documents that reference documents on said host; wherein the step of determining one or more regions associated with the host based on which other hosts contain documents that reference documents on said host includes the steps of: determining a diversity of domains in which there are other hosts that link to the particular host; determining whether the diversity is greater than a specified threshold; and if the diversity is greater than the specified threshold, then associating the particular host with a classification value that indicates that the particular host is of equivalent interest to multiple regions.
6. The computer-readable storage medium of claim 4 , wherein determining the diversity of domains in which there are other hosts that link to the particular host comprises: determining, for each domain, a relative domain frequency; determining, for each domain, an intermediate value that is equal to the relative domain frequency of the domain divided by a summation of relative domain frequencies for all domains; and determining an entropy value for the particular host as the summation of the products, for all domains, of the intermediate values for those domains and a logarithm of the intermediate values for those domains.