I've been in positions from Full Salary to Full commission/Bonus. I can tell you that when it is the latter you are relying on, there is a much greater tendancy to take risks and cut corners.
I think the main issue with the banks is not the huge Gross Income that can be gained, but that the proportion to be gained from bonuses is so high that the whole system was geared to risk taking.
As someone fully behind the free market, I have to question how any bankers, particularly at an organisation like RBS, can be in line for performance related bonuses in the current climate in view of their current situation.
That suggests to me that the contracts are ill thought out.