Have just had to set up an account to use the Dartford Crossing. Beyond the fact that they promised it would be free once it had been paid for, I don't object in principle to having an account and it saves having to remember to pay every time we cross. I do though object to the automatic payment threshold being set at £10. We only usually cross on a return journey every couple of months. The account will always be topped up whenever it goes below £10 so they will always have 4-6months worth of credit. I can't see any reason (other than greed) to set the threshold so high. Surely £4 credit should be fine unless you are planning to do lots of return trips in one day. As you can set a higher level then surely you would if you were using it everyday.
I know that we could manually increase it but that requires keeping track of when we last topped up and how many journeys we do. It is the same for their school lunches, min threshold is £10, fine if they have lunches everyday but a lot of credit if they only eat once a week, with three dc that could be £30 which is always in credit (as all have to have separate accounts). I.e. they never eat from that £10 as every time it gets down to £10 another £10 is sucked out of our account.