First of all, it's not hard for anyone to imagine the accompanying security issue, that's why I mentioned on PDF that in the 21st century cyberspace is the most critical domain, because one major, if not most important of all, basic human rights - financial/property rights - hang on it.
Then, it isn't hard either to imagine privacy issue. Having one's complete financial foot-prints in the cyberspace, that just brings the issue to a whole new level.
Cash notes are of course not perfect, but they are material IOU printed by the issuer - central bank - and no one can take that away. E-moneys are different, banks can limit, set conditions (fee) or even rightfully refuse cash withdrawal, they can do these as long as they still in-theory allow "liquidity" by electronic transfers, i.e. to another electronic account, another bank. Imagine in a civil forfeiture, no defence left.
Talking about central banks, it would definitely be much easier to implement negative nominal interests rate (NIRP). How about "real" interests rate, negative or what? Well that's just another "story" for bankers to tell, after all it's them (or their government) who publishes inflation/deflation data.
Some interesting reads:
http://www.theatlantic.com/technology/archive/2016/04/cashless-society/477411/
http://www.forbes.com/sites/frances...eliminated-the-zero-lower-bound/#c5d54e854a05