I know most RC'ers don't operate like this, but I have seen some less obvious, but just as stupid things done.
Last year we had some people flying RC aircraft about 500' off the airport where I fly, in a park. While they felt they were operating safely, since they weren't in line with the runway, they were actually right where all our helicopters make approaches from.
When a group of pilots confronted them, they claimed that they weren't causing a safety hazard, had been there all day and not seen a single helicopter. BS. I had been flying all morning, and flown directly over that spot, and we have more than a dozen helicopters often flying at the same time. Since it's on approach, I am often only 150-200' AGL at that point, and they were flying their RC aircraft at least that high.