Obviously the collection of taxes and distribution of public goods.
But the main Government intervention as far as the financial sector, should be in the control of bubbles. The derivative and credit expansions are really the main problems here and could have/should have been contained in the first place.
Why weren't they contained? There is no excuse, except that guys like Greenspan believed that even after a bubble bursts, the economy would have generated enough growth (in the bubble phase) to offset the negative impact of that burst (at least that is how these guys justify it after the fact).
No good blaming the fall guys - the momentum for continued credit growth was because of us, the general public. If Governments tried to curb people spending because they were racking up debts, they would be voted out. Treasury, even though Governments say they are independent, always take into account the party line.
And yes regulation was & still is, very poor, but still no Government wants to tackle it. Even our own Government, knowing the consequences, has set up its own sub prime lending risk just to keep the construction industry happy during the downturn. They don't want to upset anyone and that's the problem.
As I said, I still reckon the only way out is to allow a free market correction. This way, Governments aren't responsible and their role would be to ensure that our social system is maintained to assist people who fall on hard times.
Cheers