[user5994461]

>>> By using many accounts, you create clear isolation boundaries that require opt-in sharing.

In theory yes. In practice, you will achieve the opposite of that.

Developers and ops will have to juggle between 10 keys and accounts to get anything. The keys will end up saved and written all over the systems. It will be impossible to have audit between all the accounts and access.

[ejcx]

Op here. I don't think you read the blog post! Our entire engineering org has a grand total of 0 AWS keys!

Per-account isolation is great for security and especially reliability, if you run in to constant ratelimit issues like we do.