I realize that there are a couple of reasons that my opinion on this subject is not exactly enlightening, or useful--I'm relatively new to the hobby and have a zillion years of learning to do before I'd be comfortable claiming anything more than "yes, I have heard of metal detecting." Perhaps most importantly to this particular subject, I have not yet had any major finds or anything even remotely exciting, and therefore do not have a site that I feel the need to guard. But, perhaps due to those very reasons, maybe my thoughts will help out some of the friendships that are apparently being strained or even broken due to these topics.
If I'd never come in contact with this board or with others who are in the habit of guarding sites etc, I would never have considered the idea. Obviously if you're talking about land owned by friends and family, I can see that it's not something you would really encourage as an option to anyone else, but I would have basically never had a problem sharing the location of my finds if I shared the finds at all (i.e., yeah, I can see finding something in a site, and then hunting till you're happy--but if sharing the finds, I'd likely naturally share the location). It just simply would not occur to me, and I really want to stress that, because it's important to what I'm about to say.
If going along in this happy little ignorant way for a while brought me in contact with a local group, or just one or two buddies who have had experience, this issue still may not be brought up. I know that many people feel this is something that is just KNOWN, like it's only natural common sense in a particular society to apologize or express gratitude in various times. This is not the case, though, at least for me, and I imagine for others as well.
I'm not criticizing anything--just pointing out that while this may be natural etiquette to your mind, to assume this is something that everyone would protect may be causing much of the damaged feelings. It's a different personality type--my husband is very much more suspicious than I am in general, probably not more than "normal," whereas I admit to a more open nature than many others.
I also have to admit that this exact situation in the original post may go completely past me if I were the "snaky" friend. I read the post and gathered that the site is not on a private property, so somewhat open/public. If my friend TOOK me to such a site, I would assume implied understanding that this is an area I can go by myself as well, unless it were a private property where permission has been granted expressly to my friend alone. Especially as the friend did not attempt to lie or evade the question when asked--it just simply may have been something that was absolutely not intended to be a betrayal. It seems the most "wrong" was done in apparently digging up the area so badly.
Again, I'm not really much weight in importance, and while my opinion is not changed on the matter for MY personal codes, I do not argue with the concept of secrecy and the rights to maintain silence about your sites, regardless of the public access or not. I'm just trying to point out that perhaps the "snakiness" that some people assume is in place is actually the exact opposite of sly manipulation or cunning--I may have done the same to someone else without a single intention of betrayal and with only open and honest misunderstanding. In that case, I would feel terribly to have hurt my friend, and apologies would be sincere and immediate upon understanding. However, if I were not even given the benefit of understanding, I have to say that the accusations of intentional betrayal may damage the friendship from my behalf.
I just recommend giving the friends in these scenarios some slight chance. These feelings are the type that are difficult to truly take to mean ultimate bad intent--while the actions of going without you and hunting are obvious, the REASONS are not always underhanded. A friend who does not understand how you feel on this matter should not be labeled with the same label that a friend who DOES know, and still does it blatantly.