Governments can fail when they intervene in markets if they worsen the problem or create a new one, resulting in net welfare loss to society
Government subsidies could distort price signals, reducing the power of the free market which could lead to inefficient allocation of resources
Government policies might have unexpected or unintended consequences, causing failure
Sometimes social benefits of a policy might not be worth the financial cost of implementing it. If it isn't then there may be a failure
Some policies made by governments might be made decided without perfect information. However it is impractical to get perfect information so assumptions must be made which are sometimes wrong