This summer at our favorite lake, I was in camp by myself for 3 days when DH had to go back home to work. Driving through the campground the morning after he had gone home, I realized our 5er was the only rv in the park! The dogs and I were just fine, though I did let the Park Service guy know I was there alone. He and his wife came by several times to check on me. They were very nice and the closer it got to the weekend, the more folks pulled in around me. I was only concerned (not worried though) when a storm came up and the wind really howled! I was concerned that a tree limb would come crashing down. Other than that, no problems.
We camp in the National Forest as well, usually by ourselves. We can see other campers across the meadow, but most times people who camp up there alone - want to be alone. So, other than waving as they drive past, we tend to leave people to enjoy the solitude.