The private entity is more accountable because people can refuse to use it.
In theory, yes. In the real world that actually exists however, it would be very hard for a film to get released in many theaters without a MPAA rating. I don't see how the studios would be "forced" to use the government's rating if it did exist anyway. Like I said earlier, I don't think the ratings should lead to enforcements on how movies are show. The ratings would just exist on a government web site somewhere. If someone wanted an alternative system they would be free to make one themselves.
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My bracket wasn't good enough to beat SuperNiceDog's in the GameFAQS Rivalry Rumble. Congrats!
This is Yesmar.