A standalone memory device is provided that when in a first state allows data to be written to the device from a data source but prevents a normal user from useably accessing that data. When in a second state the device enables the user to useably access data stored in the device. The device is arranged to implement a prohibition or restriction on re-entry to its first state after having left it. In preferred embodiments, the device limits the number of times or the frequency at which, it re-enters its first state, whereby to limit the amount or rate of transfer of data via the memory device from the data source to a data recipient. The device can be used to limit content download from data sources at an exhibition. A system and method using the device are also provided.