@sonya I tend to doubt the judgement of spammers in general, but they seem to have an idea that it's a good idea.
If they were intelligent at all, they'd spin up their own instances and take advantage of federation so they could fast-flux more effectively to evade blocks.
@parataxis @puellavulnerata @sonya No - IP reputation schemes tend to end up either favoring centralization of resources [which is the opposite of the widely federated goal that would be nice here] or having weaknesses to sibyl networks.
The greylisting approach has had success with email, and can be used in conjunction with other counter-spam measures to mitigate many of these approaches.
There's no single silver bullet for these situations - just measures of varying effects.