I found this discussion interresting but I notice no one mentioned Monty Hall's Solution to the Monty Hall problem that he gave to a New York Times reporter when this problem first made the rounds in the early Ninties.
I found a partial interview here

I found this quote Here (a PDF)

Monty Hall declared, “Her answer’s right. You should switch.” But, after thinking about it a bit, Monty qualified his response: “If the host is required to open a door all the time and offer you a switch, then you should take the switch. But if he has the choice whether to allow a switch or not, beware. Caveat emptor. It all depends on his mood.”

Note that the problem is more a psychological one then a probabilty one...

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