Re: Cashless society ... please no !!
Handy if you want to break in someplace without risk. Check the database, see both adults are on the other side of the city from the card transactions, and carry on.
Just don't forget about the school holidays!
Using a debit card would also ruin the whole 'signing out' anti-fraud Oyster thing that stops card cloning being much use - it knows you are on one platform so it won't authorise the same card again onto the same platform. Are people going to have to re-bonk their debit card?
A debit card could do the same, in theory, but since you could go target a shop or something to skim the cards instead... not so useful. Since Oyster is only used on the bus, train or to open the door at London Hackspace, it is far harder to skim.