But would you use it to show ads if you have access to such a backdoor?
That's an easy way for your backdoor to be found out. Something like this, if it exists, would be too valuable to be used en masse.
Well if I am a secret service I could either try to force google to do it and risk a leak or I could find a way that there is something in it for them that has the benefit of providing plausible deniability?
