13. A system for facilitating advertisement selection using advertising units, the system comprising: an entity referencing component that references an entity comprising a sequence of two or more words; an advertisable unit determining component that determines that the entity is an advertisable unit that is a sequence of two or more words that functions as a unit for purposes of selecting an advertisement for display, the advertisable unit determining component comparing search data associated with the entity to search data associated with each substring of the entity to make the determination, the search data comprising at least one of click numbers, click-through rates, clicked Uniform Resource Locators, or search snippets that correspond with search results presented in response to one or more user search queries; an advertisement selecting component that selects one or more advertisements to display to a user in accordance with the advertisable unit.
13. A system for facilitating advertisement selection using advertising units, the system comprising: an entity referencing component that references an entity comprising a sequence of two or more words; an advertisable unit determining component that determines that the entity is an advertisable unit that is a sequence of two or more words that functions as a unit for purposes of selecting an advertisement for display, the advertisable unit determining component comparing search data associated with the entity to search data associated with each substring of the entity to make the determination, the search data comprising at least one of click numbers, click-through rates, clicked Uniform Resource Locators, or search snippets that correspond with search results presented in response to one or more user search queries; an advertisement selecting component that selects one or more advertisements to display to a user in accordance with the advertisable unit. 16. The system of claim 13 , wherein the selected advertisement is presented in association with a set of search results.