If spam detection relies on obscurity of the signals used, then it isn't good spam detection and for every change it's only a matter of time until spammers adap

If spam detection relies on obscurity of the signals used, then it isn't good spam detection and for every change it's only a matter of time until spammers adapt. So? It works until they do adapt, then the cycle repeats itself. There's no such thing as perfect spam prevention. It will always be an arms race. At the end of the day it's not your job to explain their reasoning or apologize for their screw-ups. If you're not a Google employee, then you've got no idea what their internal goals are or what their "job" is. There's not much content for me to address, here. My statement was pretty self-evident. If somebody behaves like a jackass, do you tolerate that person? Google isn't behaving like a jackass. They're simply not going out of their way to do other people's work for them. It's not Google's responsibility to make sure your domain is kosher; that's yours.