The currency either becomes worthless immediately ( not gonna happen) or loses value due to rapid inflation.
Much more likely could be a Cyprus-like scenario, when there is an extended bank holiday. Given that banks pay zip, nada, zilch in interest..you might feel better keeping more cash on hand..say 6 months worth..assuming you have a safe, and/or a safe, and fire-proof place at home to keep it..
Broader perspective..it makes more sense now to consider having a greater % of your assets in gold. ( I personally think the stock markets will correct at least 30% ( if not more) before the 2014 election..so again the question, if you own gold..is where to keep it...having physical possession of some ( if not all..depending on the amount..) makes more sense than ever now...again, assuming you have a secure place to keep it..
Having physical possession of any valuable asset is scary. If people see a safe being moved into your house, they know where to come.