I definitely didn't intend to blame the victims here, beyond trusting Meta in the first place.

As for security models, it's probably long since time to sandbox all data and apps. More like mobile devices. Allow users to toggle that all off so they can use their computers for development etc, but the default state should force apps/tools to explicitly ask for permission to any folder, other app, API, CLI, etc. And ask for that permission regularly (or rather, reset the permission after some period of time). Or something like that (I haven't given it a great amount of thought).

there are patterns like task-scoped authorization solutions that could help here but the integration would be tricky since Muse is not open source

I mean, it's not that the data isn't safe (they at least have modern user-level data protection similar to the other tech giants), nor will the agent generally do stuff you don't tell it to do. But I'm sure their stance was less "let's ask for granular per-category access whenever the user actually needs it" and more product-driven "we want the agent to have all the data and context it needs to become a successful product that gets people hooked, so let's ask for full disk access".

Many/most major companies have had various leaks. Plus it’s one more place for the government to go looking for stuff. So it might be safe in the sense that Bob can’t see Sally’s data. But it’s not safe in the sense that Meta shouldn’t have the data at all and can’t be trusted not to use it.