“Humans have far too many roles in life – or what personalization systems might call profiles – to possibly predict what a given user wants on that day. A woman shopping for baby clothes, a tie for her husband, and a gift for her sister may appear schizophrenic because she is acting in three different roles – mother, wife, and sister. What do you show her next? Tossing ads at her about strollers is not going to appeal to her now that she’s shopping for a new cocktail dress for herself.”