Re: Developing world?
There's no need for it in countries with developed banking industries. But it can be amazingly liberating in developing countries.
For example I was reading about minibus drivers in Nairobi. The police were hitting them for bribes every day for fictitious traffic offenses. The same happened regularly to all drivers, but these guys had loads of paying passengers, so were guaranteed to have a cash.
So a bunch got together and started only taking payments by M-Pesa. Which meant they could tell the police they had no cash - but were happy to pay the fine by traceable electronic means. Suddenly those fines disappeared, and they were able to lower their fares and not get robbed by the police on a daily basis.