Imagine a wallet for a couple. You keep both of your satoshis in a multsig wallet. When they want to spend something, both have to give access. Or, a wallet you're making for your kids, which they need your approval to spend bitcoins on. If you have a small business with a partner. You put the company's cash in bitcoin and to withdraw you need to have the signature of both.

Why not both? With something like Liana, you can have, for example, your single-sig wallet and an optional 2-of-3 multi-sig recovery path that only becomes active if you don't transact for a year. Lost your key? Sucks, but you can still get your funds by waiting a year.

complicated question given the unpredictable future usage patterns for bitcoin. as bitcoin decouples from fiat one imagines it getting harder and harder for "everyday people" to move money on chain. I argue that most people in most communities in the world don't need money like that, and these people could probably interact with the blockchain at a community or regional level rather than an individual level.

Why should we demand that people who live on less than $20/day be self-sovereign hodlers of bitcoin? We've got MUCH bigger questions to answer before we quibble over how "everyday people" can benefit from the intermediate and advanced use cases of bitcoin.

Collective treasury management, e.g. a businesses with multiple partners. afaik Most business banking solutions are equivalent to single sig where multiple people can unilaterally move funds.

I'm not sure business owners are everyday people but everyday people probably don't estate plan either.

You will potentially find use for multisig in any scenario where multiple people are involved:

Multi-sig is more robust than single-sig against $5 wrench attacks, as even under duress one cannot forfeit the keys if they are geographically distributed. This can happen to regular people, for example:

I am also interested in multisig used for those who aren't mentally well enough to manage their funds but don't want to give over full custody either (such as the elderly, addicts). Perhaps there's some kind of scheme where a trusted partner verifies the transaction as legitimate (the elderly person isn't getting scammed, the addict isn't buying alchohol, etc.)

Unless you have a very small amount of Bitcoin I think multisig is better than singlesig.

Disclaimer: I work on a multisig wallet/service.

The question of why multisig is better becomes clear IMO when we approach self custody from a comprehensive risk analysis perspective.

What is the most robust way to hold bitcoins to ensure that you can secure them not just for yourself, but also future generations? What is a way to eliminate as many single points of failure (SPOFs) as possible and to be extremely forgiving to mistakes, mental or otherwise?

We’re still in the very early phase of Bitcoin. As adoption grows, attacks on Bitcoiners will undoubtedly get more sophisticated. From phishing attempts, supply chain attacks, widespread surveillance cameras and IoT devices, to social engineering. Hence it’s worth thinking through the risks that might exist not just today, but in the near future.

Multisig also enables innovative usages such as collaborative custody, which others have mentioned here in this thread. If we think about it, Bitcoin is the first and only asset in history that can be jointly owned by multiple parties without relying on a central authority. To me this is a big deal, and a super underrated property of Bitcoin that I think people will only come to fully appreciate in the years to come. Both in terms of security and more innovative use cases. Non-KYC estate planning is another.

And I don’t believe either singlesig or singlesig + passphrase is a good enough substitute for multisig w.r.t. safe custody. Wrote more about it here: https://hugonguyen.medium.com/passphrases-are-not-the-solution-for-bitcoin-custody-4f967a339b1b

Like many have mentioned there are cases where you have multiple partners that should be in agreement of all payments. However nobody mentions what happens in the case that one of them dies? Loses access to their key, for some reason. What options are available to handle these cases safety?

I guess one possible option would be to have some sort of script that unlocks the money after a very long time with a single key, which can be cancelled by any other key, no idea if this is possible though!

For escrow services