15. A system comprising: a computer readable medium having instruction stored thereon; and one or more computers programmed to execute the instructions to perform operations comprising: obtaining aggregate document usage information provided by a plurality of users for a first document wherein the document usage information represents interactions of the plurality of users with a same specific position within the first document wherein the document usage information includes an amount of time that the plurality of users spent accessing the position in the document; receiving a query submitted by a user of a computer system; obtaining search results responsive to the query wherein each search result identifies a respective document and wherein at least one of the search results identifies the first document; ordering the search results based on, at least, the document usage information; and after the ordering, providing the search results to the computer system.
15. A system comprising: a computer readable medium having instruction stored thereon; and one or more computers programmed to execute the instructions to perform operations comprising: obtaining aggregate document usage information provided by a plurality of users for a first document wherein the document usage information represents interactions of the plurality of users with a same specific position within the first document wherein the document usage information includes an amount of time that the plurality of users spent accessing the position in the document; receiving a query submitted by a user of a computer system; obtaining search results responsive to the query wherein each search result identifies a respective document and wherein at least one of the search results identifies the first document; ordering the search results based on, at least, the document usage information; and after the ordering, providing the search results to the computer system. 21. The system of claim 15 , wherein the operations further comprise providing credit to one or more of the plurality of users wherein the credit can be exchanged by the one or more users for goods, services, coupons, monetary rewards, or access to documents.