1. In a computer system comprising a user interface configured to display content items, a method for personalizing content for a particular user, the method comprising: identifying a long term profile having one or more features in a feature set and a long term level of importance associated with each feature in the feature set, the long term level of importance associated with each feature in the feature set being based on a first, longer history of user input received from the user via a social network; identifying a short term profile having one or more features in the feature set and a short term level of importance associated with each feature in the feature set, the short term level of importance associated with each feature in the feature set being based on a second, shorter history of user input received from the user via the social network; identifying input related to the display of the one or more content items on the user interface; and using the input to modify the short term level of importance and the long term level of importance associated with each feature in the feature set to form a modified user interest set.