It's not a scam, it's a farce that they can try and 'fine' you a disproportionate amount against the agrievance caused. And that is why I will not pay. Charge a reasonable amount such as the council do and I'm sure more people would pay up.
Ok scam may not be the right word. I certainly don't think the DVLA should be allow to pass on your details to anyone other than the police or insurers though. As you say, these private car parks should make their charges fair. £60-80 for going over by a short period of time is just not reasonable.