1. A method comprising: maintaining a profile for the user at a social networking system including a processor, 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 unknown information items from the set of unknown information items at the social networking system; determining, for each of the plurality of questions associated with the one or more unknown information items, a response probability based at least in part on one or a combination of a format and content of the question, the response probability indicating a likelihood of the social networking system receiving a response to the question when presented; determining a data acquisition value for each of the one or more 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 one or more unknown information items by the social networking system based at least in part on the data acquisition values; and selecting, by the social networking system, 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.