1. A method comprising: presenting a plurality of questions requesting information items associated with data describing characteristics of a user of a social networking system; logging, in a database, a plurality of responses from the user to the plurality of questions; maintaining a profile for the user, the profile including one or more information items associated with data describing characteristics of the user and a set of unknown information items not associated with data; obtaining a plurality of questions associated with one or more information items from the set of unknown information items; determining, for each of the plurality of questions associated with the one or more information items from the set of unknown information items, a response probability based at least in part on one or a combination of questions previously presented to the user and the logged plurality of responses from the user, the response probability indicating a likelihood of receiving a response to a question when presented; determining a data acquisition value for each of a plurality of the unknown information items in the set of unknown information items, the data acquisition value of an unknown information item based at least in part on a value to the social networking system of associating data with the unknown information item and the determined response probability; selecting an unknown information item from the set of unknown information items based at least in part on the data acquisition values; and selecting a question associated with the selected unknown information item for presentation to the user based at least in part on the response probabilities of one or more questions associated with the selected unknown information item.
2. The method of claim 1 , wherein the probability of receiving data associated with the unknown information item is based at least in part on a historical response rate of the user to requests for information presented by the social networking system.