Don't they publish SLA numbers? The reliability of the major cloud providers seems quite well-established.
> There's no guarantee your cloud won't terminate your account
Two cloud providers pretty much guarantees against that -- the idea that two would terminate it simultaneously is vanishingly small.
Ask Julian Assange about that. Sure, the US government claimed he had committed a crime, but he disagreed. You really need to store your data in at least two of (a) NATO and Western-aligned countries (b) Russia and aligned countries (c) Mainland China, and that’s assuming the prior probability of you being at risk in those blocs is low. It’s hard to avail yourself of this if you’re a legitimate company, but plausible if you’re a private citizen.
But in practice everybody's data is widely distributed.
So I'm not sure what kind of event you're imagining that would take down one customer's data and no one else's.
It's not an issue. Whereas if you're warehousing all your data in a single physical location, it's vastly more likely for it to be fully destroyed due to a fire/earthquake/flood/etc.
> The idea that two would terminate it simultaneously is vanishingly small.
Au contraire, if you become sanctioned or illegal, both would necessarily have to terminate simultaneously, if the cloud providers want to comply with local laws.
You're not using a Chinese or Iranian cloud, are you?
If you have legal troubles that's a different conversation. And the feds can certainly confiscate your physical media anyways.
Or so they say. It's not like you can double-check.
> Is there any situation where it makes sense to be physically hosting backups yourself, for long-term archival purposes?
Yes, political and legal risks. There's no guarantee your cloud won't terminate your account for any of a thousand reasons in the future.