The fact of the matter is that someone is always unhappy when it comes to spam control. If the restraints are too loose then suddenly everyone is screaming about how "spammers are ruining Google" and "Google is doomed because of spam" (this was very true right before the Panda rollout). However, if Google starts to crack down, then you get more false positives and more people upset for different reasons.
Unfortunately, no pattern recognition system runs at 100%. That's not a hard problem(tm), that's an impossibility. Relatedly, I don't really see what's wrong with assiging a "reputation" to a domain name. As the article states, it's possible to climb back up to "good" status, it just takes some extra work. Kind of like in real life.