Interesting post
I think that SOME of the problem stems from people not changing with the conditions.
Tom and Adams set up is correct IMHO. size of anchor and length of chain longer than boat.
what is easy to change is the amount of warp. on a nice day, average tide 3 times depth is fine. on a strong tide and short choppy sea I increase that to 5 times to allow for the conditions.
I also use three ply nylon rope not braid to allow the stretch to reduce snatch.
Rob your advice is good, and putting on additional ties is a quick option, but not that much quicker than cutting the ties and changing the position of the usual shackle.
The other problem and the one that gives us the most problems is the sea bed type.
Near some local wrecks its clay, and a bitch to anchor, as they tend to plough a trough and as the strength of the tide increases they slip through the clay.
In other areas there are large stones that jam in the anchor as Dan describes, this not only stops the anchor working it makes the recovery with alderney ring difficult, the extra weight allows the anchor to sink again as you try to get it to the boat.
It sometimes needs to be motored out several times .
Its a frustrating thing and not recomended when putting the hook down uptide of a big wreck, so much so that I now use a 15kg anchor and chain.
I have contemplated carrying another length of chain and two shackles, so that the length of chain can be increased on those days or in those areas when the damn boat will not stay put.
Charlie