Likewise! I don't really enjoy drinking, but if you're ever in Portland, OR, let me know!
"I would say that the goal of copyright is for a creator of reproducible works to be rewarded proportionally to the value they contributed to society."
I've never actually heard this as a rationale for copyright. Even so, I don't think it holds as a justification. Because you're starting from the premise that these contributions have an inherent value. But the premise of capitalism is that the best way to determine something's value is how much others are willing to pay for it. In the absence of any restriction, these creators haven't created anything of value because it's easily reproducible. If you place the arbitrary restriction of 'copyright' on these works, then, yes, they become valuable through artificial scarcity. But that's true of anything that has very little value.
In your doctor thought experiment, you're sort of violating the basic premise of capitalism. You're also here making a deontological argument, that it's only morally right to support some sort of payment to these altruistic doctors, even though they have no actual value, since they'll work for free. In this world, how do you decide how much to pay them? In other words, how do you determine the value of their contribution?
re IP: "Can I take someone's song and perform it for money without paying them, provided I credit them?"
Yes.
"Can I burn the song on CDs and sell them in a store without paying them? Can I record a concert in HD and sell streaming access to it? Can I take Microsoft Windows, crack the copy protection, and legally sell the cracked software in an online store? If not, can I distribute it freely on a website on which I sell advertising?"
Yes, yes, yes, and yes, but no one will pay for any of it because it will be available for free.
"Notice also that a policy of free copying would introduce an arbitrary distinction..."
It's not arbitrary, though. There's a very important distinction: you can easily demonstrate your value and charge money without arbitrary legal restriction through one model, and you can't through the other.
"...it would encourage centralized software provision and draconian DRM schemes..."
Please notice that this is already happening? Why? Because it's an easier and more sure way to make money.
Centralization of software has its good and bad points. But the elimination of privacy and security are separate issues that aren't particularly relevant to copyright. Centralized computing is actually something I'm kind of worried about, but it's an orthogonal issue.*
"Two answers come to mind"
These are both great reasons! Let good discussions between open minds strive for truth in opposition! Let opposing minds passionately disagree, but remain amicable!
* I just recently wrote a post along these lines: http://blog.byjoemoon.com/post/13581915694/an-amateurs-lamen...