What Micronesian stone coins can teach us about Bitcoin

I submitted this story on another thread about how to talk about bitcoin to a 14-17 crowd, but I thought other people here might like it too. It's a tale about something that appears to be nonsensical but it's actually not at all, and it shows how weird economy can be sometimes. If you want to google more about it, the island is called Yap, in Micronesia and the stones are called Rai Stones.

Here's a true story that migh help get things started:

There's a pacific island that or many centuries, the only currency they had were round disks of a given stone. But that stone isn't exist anywhere in the island and the disks had to be produced far away and brought back to the island by canoe, making the process very hard. Because the biggest the stone, the harder they were to carry, the bigger were more valuable and by the 16th century most "coins" would weigh over a 100kg, making them impossible to carry.

But still they were very valuable, used mostly for important trades like a dowry or a home and owning just one would make you a wealthy man on the island. But since they were so cumbersome to carry, they could be traded multiple times without ever being moved: trades/gifts were made in public gatherings and everyone knew whose stone belonged to whom.

One day an islander was bringing home a great and beautiful coin that he had labored over months in the other island when his canoe flip sides and the coin went to the bottom of the sea.

Luckily everyone in the canoe survived and had seen the stone and told everyone in the island about it. So since everyone knew the stone actually existed, it still held value and could be traded like the others. Like most stones it wasn't moved but everyone knew who was the current owner of the stone in the bottom of the sea...

Some reflections:

1. Why did the villagers "decide" to use a kind of stone that wasn't available in the island? Couldn't they use a more common thing like seashells?

2. If the stones didn't actually need to be moved to hold value, why bother moving them into the island in the first place?

3. Like the stone in the bottom of the ocean, you rarely actually see the money in your bank. When you send money to somewhere else, what the bank actually moves?

4. The stones still exist today and are sometimes given as symbolic gifts in weddings but their demise as an economic system ended when Europeans started trading island goods with large quantities of stones they were bringing themselves. What piece of technology ultimately ended up destroying that economic system and what exactly did it do?