Human-robot interaction exerts influence towards the human, which often changes behavior. This article explores an externality of this changed behavior - preference change. It expands on previous work on preference change in AI systems. Specifically, this article will explore how a robot's adaptive behavior, personalized to the user, can exert influence through social interactions, that in turn change a user's preference. It argues that the risk of this is high given a robot's unique ability to influence behavior compared to other pervasive technologies. Persuasive Robotics thus runs the risk of being manipulative.