Despite the recent drought throughout the United States in certain areas where dams are built, it would be a bad idea (really bad idea) to demolish dams. Hydroelectricity is very vital and it uses the natural resources (water). It would be a shame to remove them as it not only provides power to nearby homes but it is also a means of regulating the water flow into a city or county. The risks of having dams (if it were to break or cause a leakage) are minimal to the number of positive uses for the dam.
It is a bad idea to demolish dams because that would flood the area around the dam. There are already established things below the dam like restaurants, grocery stores, and houses. You can't demolish a dam and let out all the water into the area below. You would flood people out.
Hydroelectric dams, like most things in life, have an upside and a downside. In this case it is the difference between cheap renewable energy and ecological ramifications. Banning this viable resource completely would only increase our current reliance on fossil fuels and would unsteady many global economic micro systems. On the other hand, guidelines must be put into place to weigh the ecological responsibilities of each dam. Banning the system is not the answer, but creating guidelines that will create minimal local disruption will do the least damage.
They Turn an abundant resource, water, into something we all need more of, energy, and they don't emit any carbon dioxide! I do not think it is a good idea to destroy hydroelectric dams. They are powered by a never ending recourse and don't emit any harmful or poisonous gases.