I have historically been a generous patron to VICs state revenue. And in NSW where we have compulsory third party insurance (aka CTP, the "green slip"), and private insurance companies are administering this public liability in a privatised manner, they have started taking demerit points into account in order to bolster their coffers even more. So the last VIC speeding fine from 2.5 years ago is costing me about $200 extra every year I have to renew the CTP. So in effect, a speeding fine is not just the fine amount itself, but the increased cost for insurance, which amounts to a multiple of the original fine.
The constitutionality of this practise in my view is probably not given as you're getting punished for the same offence several times, but as far as I know nobody has taken it to court. But then again, so are double/triple demerit points on certain days of the year. An offence should be the same offence - regardless of when it is committed.
The only study that ever was published on demerit points being a predictive factor for accident probability hails from Monash in 1997. Their conclusion is deeply flawed. They found that having demerit points roughly doubles the probability that a future crash is correctly predicted (it does NOT double the probability that a crash occurs). And for drivers age 50+ (my category), there was no data. It's one of the better examples of how bad statistics are used against us.