In the context of the ‘free access’ argument, there is a worrying parallel between the increase in visitor numbers to a site and the damage that can cause. Ten or fifteen years ago, for example, there was hardly anything left at the Swallowhead Spring, and what was left there was mainly a few, hardly noticeable, wicker objects in the tree. Now the place has reached tipping point (pun intended ;-) outdone only by the mess left at Stonehenge after the ‘celebrations’ there at solstice time.
In other words, as visitors to sites increase so too does the increase in tat and the erosion of those places - re: this recently photographed scene at the Rollright Stones. Most people on this board are aware of the problems of tat, and erosion at sites, and follow the guidelines of not climbing on structures or leaving things. Sadly not every visitor to a site is a Stonehead, and climbing on stones etc is seen by some as a bit of a lark - in some cases even a god-given right.
IMHO the only right thing is the intrinsic right of a site (or in the wider context our cultural and environmental heritage) to survive undamaged, and our obligation to future generations to preserve those places and things as best we can...
Personally I'm more concerned over the damage caused at places such as the WKLB where trampling all over appears to be totally overlooked.
I take your point about WKLB, though I would say that the roofed area over the main chambers has been reconstructed and that is where most people climb or sit to view Silbury and the surrounding landscape. Perhaps, as a compromise, access to the reconstructed area could be allowed while the rest of the barrow is cordoned off...