15. A method performed by one or more server devices, comprising: receiving, at one or more processors of the one or more server devices, a same search query from a plurality of users via a plurality of client devices; identifying, by one or more processors of the one or more server devices, search result documents based on the search query; providing, by one or more processors of the one or more server devices, information regarding the search result documents to the users; receiving, by one or more processors of the one or more server devices, information regarding which of the search result documents were selected by the users; determining, by one or more processors of the one or more server devices, whether a majority of the selections were selections for a particular one of the search result documents; assigning, by one or more processors of the one or more server devices, a value to the particular search result document when a majority of the selections were selections for the particular search result document, where a quantity of the values assigned to the particular search result document is restricted over a given period of time; assigning, by one or more processors of the one or more server devices, no value to the particular search result document when there is no majority of selections for the particular search result document; and using, by one or more processors of the one or more server devices, the assigned value as one factor of a plurality of factors for determining a measure of quality for the particular search result document in subsequently received search queries.
18. The method of claim 15 , where a quantity of the value assigned to the particular search result document is limited for each network address associated with one or more of the plurality of users.