What is alarming of Greece's debt is its proportion to their GDP. Of course Greece produces stuff and "impresses" others, but it is not enough in proportion to what they owe. Money can be created out of thin air as long as there are reasonable enough goods and services produced (moderate inflation), but if too much money is created without its equivalent production of goods and services you can either default on the loans or absorb this money in the economy creating hyperinflation.
Actually I have never bought the idea that more money will cause inflation, especially in developed countries (A millionare get 1 more million, would he push all the price of living material up? very unlikely)
Same for Greece: Greece GDP is only a couple of procent of whole EU economy, even issue them a loan as big as their GDP, the money supply for EU will barely increase by a couple of procent. Comparing with what FED has done after financial crisis (print 400%+ more money), this can almost be ignored
And for debt mathematics: If this year your debt is 1 million, and your production is 1 million, then debt rate is 100% of GDP, seems quite risky. But what if next year your income increased to 4 million, then from next years perspective, your loan is only 25% of the GDP, totally acceptable. So the key point here is to increase the income for next year. How to increase the income is the quesion, and income have very close relation to the loan that others can get and spend, so it's a chicken and egg problem again