I would disagree. Fault assumes neglect in this case. This is not necessarily the case. While you are responsible for any damages done to another boat if you drag and collide with it, a well and correctly set anchor is no guarantee it will hold until you are ready to leave. Mother nature will be the final determination if it will hold and unless you take a dive to see exactly what your anchored to(and do a geological analysis of the area costing several million dollars and years to complete) you can only do your best to know the area and how to correctly anchor given the location and hope it will hold.
It just depends on what the definition of the word "is" is.
1976 Chrysler 22 "CinJam"