In particular embodiments, a temporary user is able to use another's personal computing device in shared mode for a short period of time while experiencing a personalized user interface. An indication is detected that a personal computing device associated with a primary user is to be shared with a temporary user. Access to local personal information associated with the primary user is disabled if it is stored on the personal computing device. Access to remote personal information of the primary user that is accessible from the personal computing device is disabled. A personalized user interface incorporating personal information associated with the temporary user is presented on the personal computing device for the temporary user. Personal information of the primary user is not accessible by the temporary user, and vice versa. When shared mode is to be terminated, all personal information of the temporary user is deleted.