I would say anonymity is necessary but not sufficient for security. So while you might be able to devise an example that _only_ uses anonymity that can be defeated, that would be meaningless because in real life there would be other measures at work, too.

This is why Omertà–basically a vow of secrecy achieving anonymity as far as the police are concerned–is taken so seriously and why it has been such a big deal the few times it’s been broken. But Omertà isn’t the only tool employed–they use guns, safe houses, all kinds of other tools and methods to ensure their security.