Systems and methods for replacing an existing advertisement in a digital video stream with replacement advertisements that are targeted to a user's characteristics include an ad policy manager receiving a notification of an existing advertisement in a video stream and identifying users watching the video stream as it is being broadcast by a broadcaster over a packet-switched network. The ad policy manager may then select one or more replacement advertisements unique to each user and instruct the broadcaster to transmit the selected replacement advertisement(s) in place of the existing advertisement, forming a replacement video stream that is unique to that user. The ad policy manager may then track the viewing of the replacement advertisement(s) in the replacement video stream.