There are two different issues to consider when leaving your boat
on the hook: will the anchor
hold under all feasible conditions, and will someone rip it off?
Both of these issues are very location dependent, and one's decision must be made with considerable local knowledge. One can develop a good feel for the quality of the holding after a few years of experience and a little local experimentation, but judging the social security
of an area is IME a bit difficult. For instance, in New Caledonia
I have felt pretty secure re thieving as we made our way around Grande Terre. Yet an acquaintance was robbed at anchor
in the secluded bay on the east side of Isle Ouen, some distance from the nearest habitation. And again, while we have always felt quite secure in Tasmania, our dinghy
was stolen from astern of our moored boat
in the "high rent district" off Battery
Point. In both cases, a general feeling of security
brought on a unrealistic complacency and significant losses.
Note that both of these losses occurred with the owners nearby or aboard, and in areas thought to be non-threatening.
We have lived mostly at anchor for the past 25 years and don't usually worry about leaving the boat during the day, or for evening absences. However, we have never yet left the boat at anchor for an extended period, and would be worried if we should ever have to do so.