I see. You're right, but I don't think the way I've described the camera connection I made, or any camera connection I've seen in the last few years, would contribute to the problem.

All the camera signal grounds are connected together at the DVR and all the power grounds are connected together at the power supply a couple of feet from the DVR, so there are two star ground systems right next to one another. That I've never seen grounding problems AT ALL tells me this is probably nothing to worry about. This includes a couple of three year old systems where high tide actually comes up on the sand six feet beneath the floor of one restaurant, and another one where the Marina water is some twenty feet from one edge of the restaurant. If you won't have ground problems in systems so close to the ocean, I doubt you'll have them anywhere.