This is a real thing, large companies including bay area tech companies use them to graze lawns instead of just mowing. There was even a Shark Tank pitch.
And you don't get nutrients out of the soil (in the form of grass) that you take somewhere else. It's a good thing, and goats are cool (if they can't go near your car and eat parts of it.)
[0] http://www.amazon.com/dp/B00UBYDXXQ/ref=vas_sf_GoatGrazing