(Before I start this topic, I just want to say that I don't want to pick on Coinbase here specifically, but they are the biggest with over 10% of all Bitcoin being held for customers, so they are a good example--but assume here that this question could apply to any digital asset custodian).

Today, Coinbase is holding over $100 billion in Bitcoin.

While I am sure they go to great lengths to secure this money (!), we'd have to concede there is a non-zero chance they could lose some or all of this Bitcoin to theft or simply losing it.

And then what?

Coinbase offers this vague promise on their website that they are "partially insured", but does anybody know what that actually means? If they are hacked and the addresses get destroyed or stolen (we'd never know which), then... where would that leave Coinbase depositors?