This is a question I deal with almost every day - the correct answer is "we do not know". An even better answer is "we have not yet discovered the answer (and the explanation of it).
I am currently preparing the related dissertation chapter, i.e. all this inquiry on whether and how the "crisis" has affected the development and dispersion of economic aactivity without official currency in Greece. The main outline of the chapter can be found on the following presentation (in Greek)
(copy the link or open the link at the left column of the blog).
Once the paper is ready, it will also be published!
"It is astonishing what foolish things one can temporarily believe if one thinks too long alone, particularly in economics". John Maynard Keynes (1936, The General Theory).