@Logicfest -- but there are times when graphics cards are intentionally throttled back because of heating issues. Take a card that has a blisteringly fast graphics card but it is slowed down because the cooling system that is necessary if the GPU is run at full speed is very expensive.
The solution, for the manufacturer, is to make the GPU run slower so a more affordable cooling system can be used and the card can be sold to people who don't want to pay for a ritzy cooling system. In that instance, overclocking that card could lead to all kinds of problems. The GPU could handle the speed, but the cooling system could not.