I really like how people here talk about Greece's problems based on what they've seen reported on their tvs. It's quite funny compared to actually living the situation. But since the discussion went towards tax evasion, lets clear something out.
Greece has had a corrupt political system even before it became a state. Politicians don't get corrupted by themselves of course, there are many companies, businessmen and contractors kind enough to help them(with many of them located in the noble tax-paying north). So in the end, everything the state buys turns out to cost more that it actually should, from weapon systems that get delivered faulty and no one dares to ask any questions, to public roads costing 6 times what they should. (And we are not even counting the income loss from tax laws that the big players can directly influence)
Now, as a citizen you are supposed to pay your taxes and in return the greek state is supposed to provide you education, health and public infrastructure but because of all the money grubbing these three sectors were and are crumbling. You have to pay for extra tutoring if you want a dissent education for your child, you have to pay the doctors or a private clinic if you are in need of something that's less than an absolute life-threatening emergency and you also have to compensate in time and money for the bad public infrastructure.
So if you have to live in Greece for more than a couple of years you are faced with a moral dilemma: should I pay for health, education and infrastructure that the state's supposed to provide me by myself or should I be a good citizen and pay all of my taxes? Because you can't do both-it's impossible-you won't even survive. And you choose to survive.
And the question of course is, why don't people get rid of that corrupt system? Easier said than done. Politicians are smart enough to give people a few bones(remember the age limits?) and change almost always comes from something bad enough to move you out of your seat(like a bankruptcy?).
And the EU's part in all this? As it was later revealed, the big european governments knew that Greece was not prepared to enter the eurozone but for their own reasons they encouraged or at least did not react to it. And after the situation blew in our faces, instead of saying "get your shit together and then come play with us again", they were happy to collaborate with the same corrupt political system that caused the situation and give them more money under the condition that they will use it only to pay back loans (in effect bailing out french and german banks and buying time to set up various mechanisms in eurozone). Now the risk has moved from the banks' hands to the people of Europe and Greece has the same chance of defaulting as in the beginning of the crisis, if not more.
And so we(the people of Europe) are left arguing on internet porn forums. I mean, lol