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. If a trained human can recognize spam in its many forms, then it's possible for spam detectors to do the same without relying on obscurity.
Speaking on the subject, if a human can recognize that a domain is not owned by the same entity and doesn't have the same content it used to, then I don't see where's the problem in white-listing such a domain.
> At the end of the day, it's not Google's job to make your life easier
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.
> They only protect the Internet out of self-interest, and expecting more of them is unreasonable and unfair for a publicly traded company
What I don't understand is why in the world should a publicly traded company be treated any different from a real person? If somebody behaves like a jackass, do you tolerate that person? If somebody betrays your trust, are you going to give a damn about that person's bottom line?
And forget about comparisons to people's interrelationships. Why should publicly traded companies be viewed any differently by consumers and clients? Why would I give a damn if a company is privately owned or public, as long as that doesn't make a difference to my own bottom line?