The open nature of communications in Wireless Sensor Networks (WSNs) makes it easy for an adversary to trace all the communications within the network. If techniques such as encryption may be employed to protect data privacy (i.e. the content of a message), countermeasures to deceive context privacy (e.g. the source of a message) are much less straightforward. In recent years, the research community addressed the problem of context privacy. Some work aimed to hide the position of the collecting node. Other work investigated on hiding the position of an event—sensed by the WSN. However, the solutions proposed for events hiding either: (i) considered only static events; (ii) are not efficient. In this work, we describe open issues that we identified in the current research. In particular, we consider the problem of efficiently hiding mobile events.