When you encounter firms that have built parts of their subdivisions on the wrong property, or in one case a sewer pump station 2000' from the design location and completely on the wrong acreage
That's the other end of my rant. People who thing GPS units are magic boxes. You just have to buy them, read which buttons to push, then you're all set. Again a lack of understanding of what the equipment does and how it works in coordinate systems will lead to disaster. You have to check. I once established control from a known monument. After doing topo from that control and creating a surface I compared it to county wide elevation maps. It was about 100' off vertically. We did the observations again and came up with a different elevation that made more sense. We checked everything we did on the first day 5 times. There were no blunders we could find. Also the elevation wasn't exactly 100' different. More like 105.83'. The manufactures blame anomalies like this on the ionosphere!!