When you create a hosted zone in Route53 you have two options, either let them pick a delegation set for you at random, or request a delegation set upfront, whi

When you create a hosted zone in Route53 you have two options, either let them pick a delegation set for you at random, or request a delegation set upfront, which can be used when creating a hosted zone. You can create 100 delegation sets (until you reach a quota, which can be raised) per account. This would give you 100 possible combinations, rinse and repeat for more account and I'm sure you've exhausted all possible combinations rather quickly. You can also create more accounts programatically. The mitigations does make it negligible harder for someone to swoop in and take control over domains that currently have misconfigured name servers. But at that point the domains won't be resolving anything, so either the user don't care or aren't even using the domain.