1. A machine-implemented method, the method comprising: presenting a user interface for a campaign sponsor, using one or more computing devices, the user interface including a control for enabling the user to search for geographic areas for targeting content in a campaign where presenting includes presenting a search control for customizing targeting for the campaign; receiving, in the search control, using the one or more computing devices, a textual description for a targeting area to be associated with the campaign; presenting, using the one or more computing devices, one or more results based on the received textual description, each result satisfying the textual description, where presenting the one or more results includes: presenting a name of one or more geographic areas that are associated with or described by the textual description, presenting estimated reach information indicating a number of unique users to be targeted within the one or more geographic areas in a predetermined time period, and presenting 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, adds a geographic area associated with the result to the campaign, and an exclude control that, when selected, excludes a geographic area associated with the result from the campaign; receiving, using the one or more computing devices, for at least one of the one or more results, a selection of one of the add control or the exclude control corresponding to the at least one of the one or more results; and adding, using the one or more computing devices, an associated geographic area to the campaign or excluding the associated geographic area from the campaign based on the selection.