[coppsilgold]

If A adopts a Blind Signature scheme it implies A is cooperating in establishing privacy infrastructure. If A is so malicious that it would advertise a sound privacy system and then it immediately sabotages it that's a different matter...

[AnthonyMouse]

The proposals are generally to have the government do the blind signature scheme. But then even if they do so in good faith, the ad services will immediately set to work thwarting it.