The Observatory of Anonymity is a fascinating tool from Imperial College London that demonstrates just how much of a smokescreen anonymised datasets can be. The tool asks you to choose various demographic sets, displaying how each choice narrows down the chance of being identified.
Australia isn’t included, but if I lived in London my choices led from a 1 in 70 million chance all the way down to 1 in 326. Which is still enough to be anonymous apparently, but far more select - and I’m the definition of a generic person. Any slightly less average choice makes it far more precise.
As Cory Doctorow observes, the problem becomes particularly acute when two datasets are available, which allows cross-checking and a vastly increased ability to target individuals, despite the supposed anonymisation.