Perhaps it's purely anecdotal but I have heard it stated that one potential reason why the euro has maintained its value so well (and continues to) is because international criminals love it. In particular, they love the 500 euro note because it has such a high value denomination. It permits huge amounts of cash to moved around quite easily and untraceably.
Be that as it may, the use of cash is a Godsend for terrorists, criminals and tax evaders all around the world. Just think how much extra a country like Greece could garner in tax revenue if all payments were done by traceable electronic means. Just think how devastating it would be for the criminal underworld if banknotes were no longer legal tender.If a drugs gang collects up to £1m [sterling] in twenties from its clients on street corners, those notes will weigh more than 50kg - about 50 bags of sugar. The equivalent in 500 euro banknotes weighs just over 2kg.
Far-fetched, you say? Come on, practically everyone has a mobile phone. In Sweden, only 3% of transactions are done with cash since cards and mobile phones can be used so readily to pay for items. The second article below describes the latest advances in recognition technology which would make transactions super-secure.
No doubt there will be those who would see this as an extension of governmental power, a lot more Big Brother. It depends on whether you feel more threatened by your own government or terrorists and criminals, I suppose.
1.BBC News - 500 euro note - why criminals love it so
2.A Cashless Society May Be Closer Than Most People Would Ever Dare To Imagine