22. A computer system comprising one or more computers programmed with instructions that are effective when executed to perform operations comprising: assigning a unique identifier to each segment of a plurality of segments of the electronic document at a time of creation of the electronic document; determining usage indication data associated with each segment of the plurality of segments of the electronic document, wherein the usage indication data comprise a measure of time spent using the electronic document; aggregating the usage indication data for a plurality of users of the electronic document on a segment by segment basis; and communicating to a user of the electronic document the aggregate usage indication data on a segment by segment basis.
22. A computer system comprising one or more computers programmed with instructions that are effective when executed to perform operations comprising: assigning a unique identifier to each segment of a plurality of segments of the electronic document at a time of creation of the electronic document; determining usage indication data associated with each segment of the plurality of segments of the electronic document, wherein the usage indication data comprise a measure of time spent using the electronic document; aggregating the usage indication data for a plurality of users of the electronic document on a segment by segment basis; and communicating to a user of the electronic document the aggregate usage indication data on a segment by segment basis. 26. The computer system of claim 22 , wherein determining usage indication data associated with each segment of the plurality of segments of the electronic document comprises determining how much time a user spent viewing the segment of the electronic document.