In terms of whether it's "okay" to dox there isn't an "enormous" difference except in how you perceive the person being doxxed.

If you are publishing things on the Internet under your own name and your own face, it is expected that the world should know. You were yourself the person who shouted it out to the world.

If you purchase a vehicle, it is not expected that the world should know. Purchasing a vehicle isn't public speech.

In none of the above cases should the person be physically mapped or stalked. Or be the victims of terrorist attacks.