Good to see the comments on this old thread. Common sense usually wins the day, as always. I like the idea of the air horn to chase animals away - wonder if it'll work with a grizzly?
I also like the idea B-2 mentioned about starting to talk "seriously" about religion to a man who approaches and is "too friendly". After the initial approach, if feeling unsettled, immediately start **asking** questions, "Are you ... ?". If he's not religious, then it might chase him off, if he is religious, then you could have a good conversation.
Strangely, I've met a lot of people on airplanes who want to talk only about religion, but not so many when camping out. However, I might use that ploy myself (being a guy) with talkative neighbors who won't leave,
.....
When I was down in the Sierra recently, this woman came over from the next campsite and proceeded to talk and talk and talk. Said the guy she was with was a co-worker and not her SO, etc, etc. After about 25-minutes, the guy came over and clearly was miffed, and said "Do you want your beer now?" to her. LOL. I think she was having fun with the both of us.