I agree that a sensible punter does his research and all he can to minimise the risk of a bad punt but in the end if it's a bad service then the service provider is the one at fault.
Seems obvious to me.
A bad service is always the WG's fault.
The punter pays for a service and the WG is obliged to give a good service for the money, irrespective of who the punter is because she accepted his payment.
However, as we seem to have established, the more homework we do the better the chances are of choosing a good WG who will give a good service and it won't be so much the fault of the punter if he receives a bad punt for whatever reason.
Then by reducing the amount of bad punts to a minimum, ultimately the punter is not put off of punting!