[SideburnsOfDoom]

> The data you present is sufficient to prove this. Correlation does not equal causation.

As long as google keep the ranking details secret (i.e. always, with good reason) then absolute proof is hard.

You're right that "Correlation does not equal causation" but it don't discount correlation entirely either. This evidence is enough to treat the claims that negative SEO does not happen with extreme scepticism. The burden of proof has moved.

Given that there are penalties for some links, what is the mechanism that makes negative SEO non-existent? And how do you prove that this mechanism is infallible.