It is a gross infringement of privacy for personal information, that drivers are legally required to provide, to then be sold on for a profit by the DVLA.
There is also a serious risk of the information being misused. For example, violent and abusive partners will go to extreme lengths to track down former partners. Now all they need is their partner's registration number and a contact in a wheel clamping firm in order to get a home address.
To compound this problem, there are apparently very lax controls in place:
Parking firms are entitled to enfore parking regulations using wheel clamps. There seems to be no justification for the practice of selling on drivers' personal information.