Within banking, Product Control are a team responsible for the accounting and financial reporting of a trading desk. They are responsible for the monitoring of trades in the portfolios they look after, and act as a primary control function; monitoring trading activity to ensure it is within a specified remit. 
In turn product controllers are responsible for ensuring traders mark their books to fair value prices.
There have been many high-profile cases of where banks have been fined for this control not working effectively, examples including the UK's financial services regulator the FSA fining Japanese Investment Bank Nomura over mis-marking of its books. 
Poor product control procedure were also noted in the collapse of US investment Bank Lehman Brothers.