Quite a lot of members of the public have these devices in their pocket not much bigger than a packet of cigarettes which they can access the public database on.
https://www.vehicleenquiry.service.gov.uk/The only thing that bothers me is the DVLA and the flakiness of their database. It isn't perfect, although to them, the computer is always right. Even if it was 99% accurate, which it isn't, they deal in around 70 millions records (for vehicles + drivers)
Discs are a pain. They get tatty, they get stolen (Had one stolen on a motorcycle before, when asked by Traffic plod about it - I told them I wasn't going to be paying £7 for a replacement when it's got less than £7 left to run). MOT discs, another waste of time, including the old certs, plenty of scope for abuse.
It's 2014.
So to flip the question back: "How can any member of the public or anyone not equipped with access to DVLA database and / or number plate recognition camera equipment
tell if a "tax disc" is genuine or not ?"