Published online 25 November 2015.The passage of time may reverse the balance of interests involved in the processing of personal data. This provides a rationale for the so-called ‘right to be forgotten’—namely, data subjects’ right to exclude or limit the further processing of their personal information. This right has been endorsed in a number of judicial decisions in various EU Member States and has been affirmed in the recent Google-Spain decision by the European Court of Justice. To analyse the rationale of the right to be forgotten, I consider the evolving balance between legally relevant advantages and disadvantages resulting from the processing of personal data. For modelling this evolving balance, I propose a method based on the id...