1. An information processing system, comprising: a value identifying unit that identifies a value of a parameter representing a level of a ground swell of interest related to provided information, which is determined in accordance with registration of information related to the provided information; a period identifying unit that identifies, based on the value of the parameter, a period in which the ground swell of interest related to the provided information grows with a lapse of time; and a feature identifying unit that identifies, based on the identified period, a feature of a user who registers the related information.