More disconcerting perhaps was when I was with some people who were visiting the Avebury area and two of them climbed on top of the Devil's Den dolmen (albeit a reconstruction) - I freely admit I didn't say anything to them but was taken aback when they did it. For me it is an issue of respect as its unlikely that standing on a sarsen stone would damage it.
TJJ could you please clarify for me what you mean by "albeit a reconstruction"...cheers