But I don't think the intent of the lock in this case is to make federated services impossible to use properly. Clearly, the purpose of the lock in this case wa

But I don't think the intent of the lock in this case is to make federated services impossible to use properly. Clearly, the purpose of the lock in this case was to prevent third party tracking cookies. The problem is, there's no technological way to segment cookies used for authentication from cookies used for tracking in this way. The Web has an authentication problem. Existing solutions have tried to work around it by leveraging browser features not originally designed for the purpose. The result is privacy snafus like this. Google, Facebook, et al, would argue that they have platforms, and networks of sites, with a real need for this functionality, whose basic goal is not to invade privacy, but to improve enduser UX when using their services.