It's nice to see the Guardian writing negatively about the cashless push, and they hit the main points.
To me, the main danger of our time is totalitarian governments overreaching in reaction to changes in threat-actor models, and hence most of my primary concerns revolve around the particular issues that touch upon this point. There are two main issues I have with the push to the cashless society.
1. Lack of anonymity. Cash serves as a mostly anonymous medium of exchange, which encourages the free flow thereof. That being said though, one of the primary reasons you might want anonymity is from government overreach. For example, there is evidence that in the increasing surveillance panopticon, the gov wants to know what you are reading and purchasing for reading. If you use a cc to buy a book at a bookstore, that is easily tracked back to you and could in the future be used to put you on $list. While cash isn't perfectly anonymous, it ups the level of effort to find out (pulling cctv recording to correlate purchase to person).
The lack of anonymity has been my primary disagreement with Max Keiser regarding bitcoin as well. To me, I can very easily see a currency upset on the horizon which is then used to push cashless on the society as a new currency model.
2. Revocation of access/control of assets. In a similar vein to police forces using confiscation as a budgetary padding tool, I can far too easily see the same being applied to cashless currencies. More than that though, is the ability to access the option at all in the first place. As an example for this, I give you the national bank blacklist database. For some people, suddenly being blacklisted by banks can create all kinds of problems, because much of our society relies on banking functions. I fear the same type of blacklist with little oversight could be applied to a cashless currency, to the point that, lets say you were a dissident, suddenly you lose all your money and can't open a new account. If everything is cashless, how do you buy bread?
The article itself touches on the surface of these matters, but I think there needs to be a much deeper and deliberative discussion about the potential dangers, and benefits, of the push towards a cashless society.