A frustration of archaeology is the fact that while we can easily identify places where people left things, we can't always identify places where they intentionally didn't. A place that is devoid of artifacts or features because it was a forbidden place, a sacred space, or a contested boundary between two potentially hostile groups of people looks pretty much the same as a place that is devoid of artifacts or features because people just didn't bother going there out of general mundane disinterest.
To be certain, there are places where we can tell that a lack of features or artifacts is an anomaly - a lack of archaeological sites around a spring in an otherwise arid environment is pretty strange and is likely to grab our attention. But a lack of sites around a stream in an area where there are several other sources of water? Well, that could be intentional avoidance or the intentional clean-up of artifacts, or it could just be that nobody bothered to go to the location because, hey, it's just another stream.
This becomes important because of the basic purpose of archaeology: to investigate and explain the past of humanity based on the material record. Through ethnography and history, we know that there are places where people did not leave materials because either the place was actively avoided or because the area was intentionally not "polluted" with artifacts and other materials. Knowing where these places are is valuable because it can help us tease out information regarding the ways in which humans interacted with their environments, and in cases where areas were left empty for social reasons (such as the previously mentioned borders between two groups) how they interacted with each other.
Which leads to the obvious question: What's an archaeologist to do about this? There are many answers, some better than others.
One answer is to try to determine what areas would have been left empty based on some set of criteria. At it's best, this method produces predictive models based on resource distribution, known site locations, and criteria relevant to the area based on what has been previously learned, and then look for places where sites should be, but aren't. At worst, you get new-agey bullshit nonsense like this. But even at its best, all that this approach can do is tell us that a given place has a higher likelihood of having a site than not, but can't tell us if it's lack of site is due to intentional disuse or simply a bit of random chance.
Another approach, and one that can be used in conjunction with the previous one, is to use ethnographic data to figure out what areas were "left intentionally blank" rather than simply not occupied. Ethnographers have collected huge amounts of information regarding the lore and habits of the descendants of many of the people studied by archaeologists. When such information exists, it can be used to help make sense out of blank spaces, but it must always be remembered that even when the information gathered by ethnography is correct, it always reflects the time in which it was gathered and may not reflect the past.
Regardless of the difficulties, I don't know that there is a good solution to the problem, just varying degrees of dubious effectiveness. It's a fascinating idea, it makes you think, but it is also a bit frustrating. Regardless, it is something that we have to keep in mind when we are performing both research and fieldwork.