But you say this Trojan horse, or at least the examples that you have obtained, is benign. So why worry?

As far as we know, this Trojan horse is benign today, but nothing prevents a malicious hacker from using this same technique to create a dangerous Trojan horse. We have examined the code contained in this Trojan horse and it doesn’t delete any files or change anything in Mac OS X, but we cannot be sure exactly what this Trojan horse is doing now, or whether it will have other effects in the future. In any case, protecting users now is better than responding too late, especially when we are aware of the threat.