According to the Guardian,
Police are urging Greeks to keep their money in bank accounts rather than putting it at risk of theft, amid further uncertainty about whether the austerity-struck country will remain in the eurozone....
Greece's national police spokesman, Thanassis Kokkalakis, told Reuters: "Many people have withdrawn their money from the banks fearing a financial crash, and they either carry it on them, find a hideout at home or in storage rooms.
"We urge people to trust the banking system, leave their money there, or at least in a safe place, not hide it at home, where they must anyway take the basic security measures."...It appears that the money in the Greek banks is also at risk of theft. Theft by the EU by forcing Greece off the euro and back onto the drachma.
The question that a Greek depositor faces is which has lower risk: their mattress or the bank.