All layer-2 protocols (including Ark and LN with channel factories) require unilateral exit to remain 'trustless.' However, as more people use them, there are fewer opportunities to perform that exit among untrusting parties, thus bringing us back to the same problem: trust is introduced.

For example, if we use channel factories to scale so that individuals use an on-chain transaction once every 6 months on average, we can get many more people on-chain. But that means, on average, each person can't make another transaction for the next 6 months, including exiting the channel factory if a peer goes offline or maliciously force-closes, which most will find unacceptable to hold their money. So, the implication is that each person needs to trust the rest of the peers, which we can facilitate better outside of layer-2 protocols. 

 Good points. This is really challenging topic 

 I agree it's not something most Bitcoiners want to discuss because it leads to questioning the “don't trust, verify” ethos. But I think taking that mantra too literally has always been problematic because most people will never verify all of the hardware, firmware, cryptography, and source code they use for Bitcoin.

But Bitcoin has always allowed something still very powerful, if not as catchy as a slogan: “Choose who you trust.”

That's what we're doing with cashu. 

 True