Indeed, speculation has run rampant since deposed Greek FinMin Yanis Varoufakis opened the floodgates by telling a UK newspaper that the government was ready to go the "California" route with IOUs. Just yesterday Kathimerini reported that Athens was preparing to launch a parallel scrip in order to meet its obligations to pensioners and public sector employees and anecdotally, there's some evidence to suggest that Greek businesses are in the midst of reverting to the drachma as we speak.

As a reminder, the image below was sent in by a tourist who went to a cafe in Greece where the menu prices appear to be back in Drachma: