If there was a magical duplicator ray, governments would want to heavily regulate its use. A few million extra bodies would completely crash an economy, but might be good if you wanted to fight a war.

I do think the duplicator ray is a great analogy. There would be a lot of tricky moral questions raised if such a technology existed.

On the topic of a human mind in a computer, i dont think they should be afforded property rights either. If you can copy them into 10 bodies, and each one can own a house, then they are taking real resources from actual humans. This extends to owning other things too.