Unless things have changed or my memory's not so good, Verified by Visa's servers are operated by multiple individual banks and payment processors (or entities

Unless things have changed or my memory's not so good, Verified by Visa's servers are operated by multiple individual banks and payment processors (or entities acting on their behalf) -- there isn't a single point of attack. And -- again, IIRC -- VbV or SecureCode aren't necessary to the successful completion of an online transaction. Taking down these services would frankly be a favor to consumers, as 3D Secure is an extra step that they don't need.