The FCC have published details of the enforcements undertaken in 2012.

In the past quarter (October-December 2012) the FCC took action in:

1 Repeater-related case
9 General infractions (including unauthorized operation)
0 Power-line cases

In the UK Ofcom stopped publishing figures about what they do, or don't do, regarding spectrum enforcement over 3 years ago. Perhaps it can be speculated the reason Ofcom stopped reporting the statistics is because they stopped doing any enforcement ?

The last statistics directly relating to Amateur Radio enforcement were issued over 5 years ago and have since been removed from the Ofcom website. They showed that in 2006/7 Ofcom just wrote a single letter to someone who had been persistently jamming a repeater asking them to please stop doing it. There were no other Amateur Radio enforcement actions reported.

It appears it's not just radio amateurs who suffer from Ofcom's lack of spectrum enforcement. A recent survey of the Broadcast FM Band (87.5-108 MHz) in London showed that the capital city had 28 pirate radio stations broadcasting on regular schedules. It is clear that the vast sums paid by commercial broadcasters for their FM licences doesn't buy them any protection from interference by pirate stations.

Details of these actions are published on the FCC website - http://transition.fcc.gov/eb/AmateurActions/Welcome.html

Ofcom Spectrum action statistics - http://stakeholders.ofcom.org.uk/enforcement/spectrum-enforcement/stats/