Metadata and the law of unintended consequences

The Federal Government's proposed new law requiring telcos and ISPs to retain their users' metadata for two years has kicked up a stormy debate about the right to privacy and how much of it we should be prepared to surrender in the interests of national security.

As always happens when a government introduces legislation in a hurry, particularly when the government itself hasn't yet worked out what that legislation is supposed to mean (noting here that exactly what data must be retained hasn't been defined, and that the Attorney General clearly has no idea how to turn on a computer let alone tell us what "metadata" is), the effects of this new law are only just starting to be understood.