Ann Cavoukian is the Information & Privacy Commissioner for Ontario, Canada. She writes: Since the recent revelations of the NSA’s sweeping surveillance of the public’s metadata, the term “metadata†has been regularly used in the media, frequently without any explanation of its meaning. Metadata’s reach can be extensive – including information that reveals the time and duration of a communication, the particular devices used, email addresses, or numbers contacted, which kinds of communications services were used, and at what geolocations. And since virtually every device we use has a unique identifying number, our communications and Internet activities may be linked and traced with relative ease – ultimately back to the individuals involved. All this metadata is collected and retained by communications service providers for varying periods of time and, for legitimate business purposes. Key questions arise, however, including who else has access to all this information, and for what purposes? […]