Google bans for blackhat -- how deep do they go?

I've heard of Google banning sites for breaking their guidelines, like blog comment spamming with xrumer for instance. Does anyone know how far the ban extends? For example, say I have a site that I'm pushing to from 10 sites that in turn are fed with massive xrumer runs, will Google ban my feeder sites because those are what were being linked to by the fake blog comments, or will Google look up the chain and ban the target site as well? Any insight would be helpful. Thx.