I have a reasonably good idea of how many rock pile sites (sites per square mile and piles per site) can be found around here in Middlesex County Mass. There are lots and lots of sites but I find myself wondering: how come there are not more? Were rock pile sites made by a small number of people over a longer period of time or a large number of people over a short period of time? Based on what I see, it appears more like what would be the result of a small number of people over a small period of time. I would say every site I have seen could be accounted for by about 100 people building a rock pile once a year for one lifetime, or a smaller number of people making more, or a larger number of people making fewer. But it does not really add up to as much activity as I would expect from pre-history. Add to this that in the only documented information about this (at Bannock Point in Ontario) the modern day Native Americans deny having built the rock piles.
It also is part of my thinking that rock piles are ephemeral - they last for a few years and then are destroyed by natural random processes. You can see this happening at almost every site: piles bashed by falling trees, rocks around the base of a boulder which still has a few rock on top, etc. Also, as evidenced by the second excavation discussed in Manitou (the one about the "Dairy Hill Monolith"), there are other rock piles buried under ground where you cannot see them. So maybe there are lots more piles there than we realize.
Another possibility is that a rock pile ceremony might have required destroying an old rock pile before building a new one. In that case the numbers are consistent with a small group of people (perhaps the "shamans") making the piles. Or perhaps youths seeking visions would build a number of piles but these would then get destroyed, intentionally or randomly, at a rate that matched the rate at which new ones were built.
Actually the data is kind of different down in Holliston and Hopkinton at the sites Bruce McAleer located. Those sites go on for miles with thousands of rock piles. So it almost seems like a different story. There, I suspect the piles are being renewed by local Indians or were until recently. Maybe that is the explanation: so much development and destruction up here leaves a very patchy record that it is mis-leading.
All these things are confusing and worth thinking about occasionally.