Not just witnesses, but stakeholders can also be targeted. Let's say the top 20 witnesses AND the top 20 stakeholders are targeted, at the same time, in a sophisticated coordinated action.

Excellent point. This potentiality certainly warrants analysis and consideration.

Regarding attacks on stakeholders, I think the biggest advantage will be having those stakeholders distributed amongst different jurisdictions. Of course we have no way to coordinate or effectuate that — it is what it is.

As far as hosting services taking nodes offline, having 400 active witnesses should ensure that the blockchain keeps functioning even if a widespread coordinated attack came along that vector.

There are such sophisticated actors that have huge technical capacity and IT personnel at their disposal.

True. However, even if such actors were able to pull off a wholesale takedown of the blockchain and all its witnesses, Hive can simply be reborn, like a Phoenix from the ashes, as long as at least one node, somewhere, has the pre-attack history of the blockchain stored on it.