I was there a few months ago and yea, there was junk everywhere. No campers in the middle though. That would really piss me off. Are they so selfish that they don't understand they are spoiling the monument for its visitors?
Why do the Nine Ladies attract this? I also went to Stoke Flat, Doll Tor and Nine Stones Close the same day and found no problems at all.
I'll tell you another circle that attracts messy party people - The Druid's Circle of Ullverston. Poor thing!