My experience is that few people are likely to behave properly in the collection of fiddleheads from the wild. Most people seem to take the scorched earth approach: leaving nothing behind. We seen that in the Seattle area with the decimation of wild mushrooms.
In my Japanese foster family, we gathered the fiddleheads of bracken every spring. They made quite a delicacy. Taking bracken fiddleheads didn't stop this weed from it's journey towoard world conquest.
However, most of our ferns but out fronds but once a year. They are not "cut and come again" plants. Just breaking a new fiddlehead on one of my garden ferns is painful to me.
I don't eat my garden ferns and I don't forage in the wild -- there is too little wild left to support the hordes of our bi-pedal population.
I live on haida gwaii... Northern B.C. I note you said you can eat bracken fern fiddleheads... the original article says Ostrich Fern only. We have zillions of Bracken Fern here, but I have been unaware that I could try them.
Bracken fern may be edible, but Ostrich fern is superior to bracken. Plus, Ostrich fern is a lot easier to identify -- because of the groove that happens to run the length of the stalk.
As for those who will take all of the plants that happen to be in the area those people are "working" -- when you see them, just tell them that taking everything and leaving nothing behind is not only "bad form" (it leaves nothing for the next year's harvest, period), it is rude and shows them to be nothing but greedy pigs.