Tourism has been their mainstay for over a century.
... & non-payment of taxes!
Basically, Northern Europeans play by the rules & Southern Europeans try to ignore them.
I seriously doubt of a Greek default will affect world markets etc... as everybody has been expecting it for some time.
It's about time they grew up & started paying what the owe though.
A couple of facts that emerged during the start of their problems.
Greece has more owners of Porsche Caymens, than any other Euro state & less than 4% of Athens residents claimed they had a swimming pool (until the government used Google satellite to show them otherwise).