Aye i've been there, great place and luckily no idiots about on my visit.
It's a shame we have to have those horrible looking fences around the monument but i fear without them many sites would suffer at the hands of fools like these.
I remember on a visit to Stanton moor and the circles there, a group of German tourists trying to balance on the stones of the Nine ladies, when i tried to point out the error of their ways all i got was abuse, i sat on one of the stones to spoil their plan and refused to move and was threatened with violence, luckily a group of the protesters appeared just in time and backed me up.
They were also planning on having a fire on the ground under the votive tree, a threat to bring up another dozen people from the protest camp put a stop to it but it shows what what stupid things people will get up to at our ancient sites when no one is there to challenge them.
I recently lead a group of 16 people around the Stanton / Harthill moor area, none of the group had been to a circle before but there was not a hint of anyone wanting to do anything out of order whilst there, it makes me wonder about the mentality and mindset of some people.

In the 1st one i'm the guy in front leading.
http://uk.youtube.com/watch?v=TcWN8iGg1TQ
http://uk.youtube.com/watch?v=HgqoNq_4XYw