There’s always a point where the amount of data makes it a different thing altogether. Like the difference between hearing random strangers talking on the street, and have a full record of everything that person said outside their home for the past 5 years.
That depends. We could set standards for what information is linked to that plate and to whom it is accessible. (My state actually has a standard for some info which should not be tied to a plate, but they do it anyways. But nobody is going to stop them. I brought it up to the AG's office, but they were complete idiots about it)
One could also set up an anonymous LLC and register the vehicle that way if they really cared.