14. A non-transitory computer-readable medium comprising instructions stored therein, which when executed by a machine, cause the machine to perform operations comprising: presenting, using one or more computing devices, a user interface for a campaign sponsor for customizing targeting information for a campaign including a search control for discovering areas for targeting; receiving, using the one or more computing devices, user input in the search control including a textual description of an area to target; presenting, using the one or more computing devices: one or more results that satisfy the textual description, estimated reach information for each result, each result representative of a geographic feature that can be targeted in the campaign, wherein the estimated reach information for each result indicates a number of unique users to be targeted within a geographic feature associated with the result, and a limited reach indicator based on a confidence level related to available estimated reach information; presenting with each result, using the one or more computing devices: an add control that, when selected, is configured to add a geographic feature associated with the result to the campaign, and an exclude control that, when selected, is configured to exclude a geographic feature associated with the result from the campaign; receiving, using the one or more computing devices, user input to select at least one of the results corresponding to a geographic area, wherein the receiving comprises receiving user input to select one of the add control or the exclude control associated with the at least one of the results; and adding, using the one or more computing devices, the geographic area to the campaign or excluding the geographic area from the campaign based on the selection.
19. The non-transitory computer-readable medium of claim 14 , wherein the confidence level is determined based on a location derived from an IP address of a user.