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.)