Edit: BTW, I'm not saying one needs to be 100% cash. I use credit cards too. The important thing is that I have a choice.
Cash is instant, does not require power, does not require connectivity, and no one takes of cut of the transaction.
Cash also leaves a trail so faint that it requires a substantial investment in resources to trace it.
I think those hurdles will be difficult to overcome in order to match the benefits of cash in an electronic currency.
Generally speaking, the likelihood of these things happening is pretty small, and unless you carry a huge amount of cash, the cost if they do happen is not very significant.
If you are being negligent with your credit card you loose everything. If you are being negligent with cash you only loose what you have on you.