I identify the location of as many sites as I can, usually doing it when a site is already pretty badly damaged. I am more hesitant to identify locations of genuinely delicate sites, with piles in good shape. But how many of the sites already documented on this blog has anyone been to? Probably none. In general, I have a hard time imagining someone deliberately following directions given from here to a rock pile site, only to kick over a rock. Not only does it make no sense that anyone would bother, as a matter of fact no one has bothered.
It is not the publicizing of a site which threatens it, because vandalism is opportunistic. People don't go looking for sites to vandalize; instead they stumble on them and get destructive. The only example of this I have seen was my own fault: I cleaned off a pile near a public trail and someone noticed it, noticed the other piles, and decided to pull one apart. I think it was kids that did it. And kids are not reading this blog. But anyway, cleaning piles near trails and worse yet, making new trails to sites should be avoided to reduce opportunities for vandalsm.
I honestly don't think publicizing sites has much to do with it, however out of respect for the sites, and also out of fear that delicate sites will get damaged un-intentionally by visitors, I'll keep quiet about the location of the most delicate and special places.
Update:Jim P points out in comments that the greatest risk to sites is from neo-pagans trying to re-use a site for their own reasons - leaving a mess and destroying the site in the process. This is worse than vandalism, it is cultural theft. But I am going to stick to my guns to the extent of posing this question: were the sites Jim mentions ruined because of publicity or because a trail led to them? In my experience, neo-pagans do not go off trail much. Maybe they are lazy or maybe they are afraid of the actual woods. So I guess I am claiming sites are protected not so much by their secrecy but by being in-accessible. I don't propose we do a study of such things but perhaps I should repeat that making sites public has a significant upside in terms of public awareness. I argue that people who know a site's location are not in the clear just becase they keep the site secret - because they are helping preserve a status quo which includes continued destruction of sites by the construction industry - something much worse, much more systematic and thorough than any neo-pagans.