There is still an easy way to get a round of applause from the BBC's Question Time audience. A simple mention of the word "bankers" in a spiteful tone is all it takes.

Last week it was a tactic deployed by the Scottish actor Alan Cumming - perhaps best known for playing a Bond villain. Having been repeatedly slapped down by the former Scottish secretary Michael Forsyth on various points, Cumming attempted to fight back by pinning the entire eurozone crisis on "bankers". The studio audience in Inverness duly performed its role: vigorous hand-clapping ensued.

There's no doubt about it - banker bashing is still a popular national sport. To play the game properly, however, one needs to know which banks and bankers deserve bashing most.

Spain's banking sector is this weekend at the epicentre of the euro crisis. Its banks need anything up to €100 billion (£81 billion) of new capital to plug the gaping holes in their balance sheets. Until Madrid last night agreed to ask for an international bailout, it was unclear where that cash would come from - and that uncertainty had raised the eurozone crisis to new levels.

Yet the lesson to be drawn from the crisis is the opposite of what many may think. Spain's banking problems are nothing to do with the global spread of its two giant lenders, Santander and BBVA. Nor is it anything to do with investment banking. The Spanish crisis is actually a tale of what happens when power-hungry politicians get their hands on financial institutions.

Spain's problem lies with its regional savings banks - the cajas - that lent money hand over fist to the property developers that fuelled Spain's boom. Almost all of these banks were controlled or influenced by one of Spain's local governments. The party in power would own voting shares in its local caja and sit on the board. Nobody in Madrid was paying much attention to how that relationship between local banks and local politics played out.

The cajas weren't too big to fail, they were too small to bother with - and too numerous. Until the Bank of Spain started smashing them together in a series of forced mergers there were about 50 of them. Now there are 10.

Investigators probing the caja loan books claim they have already uncovered some alarming stuff. Here's a typical scenario. A local developer that gave donations to local politicians would win public sector construction contracts from those same politicians. They would then fund the projects with loans from the pet bank in question, on extremely generous terms. Or so the story goes.

David Fuller's view This problem extends way beyond Europe and the UK. For instance, plenty of provincial banks are at the centre of China's property bubble.

If Canada, Singapore and a few other countries can regulate their banks effectively, so can the rest, unless those near or aspiring to power choose to perpetuate the pork barrelling scams. Governance is everything.

(See also Eoin's lead item below on the Spanish bank bailout.)