It is also likely that defenses for this problem will prove useful against
proposed data retention plans in the EU and elsewhere, since these schemes
will likely rely on the same technology.
Sadly, it's gone beyond the proposal stage in Australia - starting on 13 October 2015, every Australian ISP must retain certain records for two years: source, destination, date/time, duration, service type and features, subscriber, and service location.
For the specific details of the minimum required dataset, see:
Of course, many ISPs will retain much more, either inadvertently, or to make sure they can satisfy any government requests.
For a general, heavily promotional view of Australian government policy on data retention, see:
(The Australian Attorney General's Department website disables scrolling and shows an amusingly inaccurate banner when JavaScript is disabled. I've asked them to fix it, but they're struggling to use their own external complaints handling process.)