The root cause of the trouble in Greece has been an overly-generous state (high salaries for public servants, generous pensions for retirees), along with tax evasion being a national sport.
I'm not sure about the situation in Italy, but whilst they've got an enormous national debt, the budget deficit is actually smaller than in Germany. Theoretically it should be affordable if the markets weren't so jumpy. Berlusconi really didn't help.
The PIIGS, the UK and a few other countries are running austerity programmes, which have meant a reduction in government spending, though I'm not sure that the British example is as strict as it's being sold as. In addition, the younger and newly qualified members of the working population are struggling to get into work as there are fewer jobs.
So I believe that youth unemployment is mainly a side effect of political and economic conditions.
One of the causes, particularly in France and Spain even before the GFC, was that the level of protection for workers was so high that it was virtually impossible to sack someone or make them redundant.
An idea that has been gaining traction in the EU is
flexicurity, which is the Scandinavian approach to the labour market. Workers can be dismissed relatively easily, but a generous social safety net exists. This means that employers can adjust their staffing levels quickly in response to economic conditions, and employees won't suffer too badly if or when they lose a job.
