This is also a problem in Australia where prescriptions are not recorded and analysed, so doctor and chemist shopping is easy.
Pseudo-ephedrine -used to make drugs at home-is monitored and so it is able to be controlled to a large extent.
There is talk of a national data-bank of prescriptions for pain killers as well, as oxycontin is a big problem.
I think it's a good idea. The doctor can check up on your record, as can the chemist.