Interesting that most of the responses have been concerned with the safety & noise comfort of the operator of the genny with not much concern about how far is far enough to the next camper?
On a quiet night genny noise is going to carry a long long way. The next camper, who happens to be running his own, won't hear it. The tenter, or other other not sound insulated camper, will.
We all know how far the sound of somebody mowing the grass somewhere in the neighbourhood travels on a quiet day.
True, distances will very depending on genny & RPM it is running but still the noise will travel & there will be those who will not appreciate hearing the drone of a genny at 3AM.
