Using six case studies - including the public transport chip card and road pricing - readers are confronted with their digital identity that they carry with them on the street. Everyday actions such as paying money, walking through the public transport gates and entering an office are increasingly recorded. As a result, our virtual identity is becoming richer and richer. The number of parties using it is also increasing. And the purposes of systems are expanding all the time. The book Check in / Check out poses critical questions regarding the digitization of public space. How much personal information are we willing to divulge and what should be in return? How far are we willing to go? Do we want to turn our city into a 'virtual fortress with a digital moat'? Will privacy soon still be a tenable concept? Or will there be a growing need for digital silence zones where you can still be anonymous? Especially if we can soon be followed live and our information can be viewed in real time by third parties? Check in / Check out formulates twelve design principles of this new phase in our information society. The authors advocate taking the user as the starting point for managing his own identity. Let him check in when he wants to be recognized and check out when he wants to be anonymous. Let the user decide what requirements information systems should meet. This is crucial to ensure that ICT systems such as road pricing and the public transport chip card are not seen as a system imposed on him by the provider. Now is the time to have this debate to ensure that the digital net does not capture us but empowers us.