BANKS often face conflicts of interest when it comes to advising their customers.
The regulators who are supposed to stop the abuses that can result are not always up to the job.
But when wrongdoing does finally come to light, the penalties can be vast.
Financial institutions in Britain have had to lay aside 40bn pounds ($52bn) to compensate customers mis-sold payment protection insurance.
Wells Fargo was fined $1bn by American regulators and ordered to reimburse the people to whom it had sold useless insurance or mortgages with inflated fees.
Now it is the turn of Australian banks to face a reckoning.
A royal commission has exposed a litany of abuses.
Its interim report, published on September 28th, paints the country's financial institutions as consumer-crushing oligopolies.
Lenders charged hidden fees long after providing services, and for some services they never provided at all, on occasion to people who were dead.
They siphoned off at least A$1bn ($720m) of compulsory pension savings in excessive charges.
And they offered mortgages that they should have known were far too expensive to afford.
Their behaviour, said Kenneth Hayne, the head of the inquiry, was not just immoral, but criminal.
The banks have tried to pin the blame on a few rogue staff. In fact the wrongdoing was pervasive—and turbo-charged by government policy.
Until relatively recently few Australians sought financial advice. But the introduction of compulsory private pensions in the 1990s gave them savings to invest.
At A$2.6trn, Australia's superannuation pot is now one of the world's largest. It has sustained a swelling wealth-management industry.
The inquiry levelled sharp criticisms at outsized commissions.
These, it found, had encouraged financial advisers to direct customers' savings towards high-cost,
poorly performing funds and insurance providers to sell policies that would never pay out.