In the United States, corporations are people. A movie like The Corporation is highly critical of this, and in a reductio ad absurbum, concludes that the corporation as such can be diagnosed with psychopathy. The movie is loaded with arguments against corporate personhood, but as a documentary, does not attempt to be neutral. On the other hand, a frequently quoted conversation with Mitt Romney, as quoted by The Washington Post:
“Corporations are people, my friend,” Romney said.
Some people in the front of the audience shouted, “No, they’re not!”
“Of course they are,” Romney said. “Everything corporations earn ultimately goes to people. Where do you think it goes?”
Leaving a discussion on what Romney means aside, what arguments can be given in favour of treating corporations as legal people?
Edit: As per DVK's comment, corporate personhood is apparently not limited to corporations. A question who it applies to is rather legal than political so probably off-topic, but answers that are broader and cover not only corporations, but also other non-living "persons" are certainly welcome.