Aside from the issue of unmarked military zones, restricted areas, pipelines and unmarked private property, there are also the sociological issues that a reviewer who has never been here can not grasp.
For instance, as we recently experienced in the cache "Evergreen", the cache was placed in an area that would from a map view seem perfect to the reviewer, however as any cacher from the area would know, the entire area is combed over on a daily basis by cleaning crews who would destroy the cache without thought (in this case causing the loss of a geocoin in the process), the cleaners can not be reasoned with or told about the cache either as there are language barriers as well and the worker's fear of deportation for a minor slight ( which is a consistent issue in this country). How would a reviewer with no experience of the area know this?
If one were to look at the issues raised by the "End of civilization" cache, the cache was covered within days by the ever moving sands of the desert, meaning that since placement, it has been found twice, to a reviewer the cache seemed fine, but to anybody who has dealt with these sands know, placing a cache under a rock on the desert is not a fully viable hide.
I do not in anyway say that Erik is not a good reviewer, I believe that he is doing the best he can, however there would be much greater advantages I feel of a reviewer who has dealt with this area first hand.