The window is a border between private space and public space. Floor-to-ceiling windows give apartment residents an excellent view to the outside, but also provide people outside a great view of the inside. That presents a privacy issue.
Why do people fear the invasion of privacy? Is it because they fear that the public will piece together fragments of their personal information and figure out who they are?
A QR code has been placed on my apartment window, viewable to people standing outside. By scanning the QR code, viewers can enter my virtual room. In this room, they can identify what kind of person I am and what my life is. Different people may find various clues in this room and may reach different conclusions.