Dangers are not really much different than the 'old' ways of getting gas and oil - they are still drilling, casing and cementing a well in the ground, then fracturing it (which has been done for decades already), then producing it into a pipeline or tank. True, the fracturing portion of the operation generally uses more pressure, water and chemicals than more traditional oil and gas production, which generally means more waste material to dispose of.
Truely, the main danger is from spills on the ground surface, simply because there is more activity going on. This can be the result of poor handling/ training/ maintenance or accidents. Dare I say that all of those can be prevented with proper planning and execution of the operations.
Companies don't want to spill things or impact the environment because it costs them money - wasted chemicals spilled, clean-up costs, fines?, compensation, paying for down-time for employees and equipment, public image affects stock price, etc.