By 
Humans are getting closer to being able to manipulate gravity, but the question is can we trust humanity and its warmongering tendencies? Hell, I don’t; and you? But as I speak, I have a brother who is a US Marine, on a flight contract, who is temporarily reassigned to guard the Syria-Iraq border. Being able to manipulate gravity could come in handy, lifting a car off the ground, which has a suicide car bomb, then turning the machine off and dropping it to the ground. In fact, the idea is so enticing that it will surely be used in human conflicts; that is, the killing of our own species. Unfortunately, it is for this reason that such wonderful technology must be well protected and agreed in advance on how it will be used.
Once such a technology exists, you can imagine its destructive power in the wrong hands, like an international terrorist lifting a bus 100 feet into the air and dropping it if his demands are not met. Or a nation wishing to serve their political will by taking a giant rock up to 100,000 and towing it to a neighboring nation state over which they have a disagreement? Those are not such pretty thoughts, but they should be considered as we advance our technologies to be used in aircraft, transportation construction.
If you consider building a building without using dangerous cranes or saving people in a burning building by lowering them safely to Earth, you can see the advantages. No more traffic, cars can fly. No inefficient aircraft as they fly where they want to go and descend instead, saving fuel to climb and land. No more worries about launching satellites or putting colonies into orbit, as they could float effortlessly and more easily than launching a balloon. Mining the moon would also be easy or snatching an asteroid and putting it in geo-sync for the necessary materials. We could launch a spaceship the size of an aircraft carrier and go visit our neighbors all over the solar system and find out everything we want to learn. Learning from other worlds and life of all kinds.
Here on Earth we could collect large ice cubes and put them in dry or drought-stricken lakes to provide water for our people and for those areas of the world, which have outgrown their water supplies due to population growth. The potential of such technologies can save fuel, reduce pollution, provide water, help with the materials we need, and make transportation safer. Now, we also have to consider their unfortunate uses due to the fact that humans are still a warring species and can use such technologies for things that aren’t so noble. Think about this.