> Who is arguing that one should pay for every previous idea that a new idea is derived from?
IP limits production to create artificial scarcity. No matter how you look at it, after you copyright or patent something. You are limiting what can be created in the world.
> As a society, we discovered that rewarding producers adds to the useful aggregate more than just hoping that they'll add the same amount of content without compensation
No we did not. Historically, Intellectual property was created as one more monopoly privilege for the monarchy. [1] Together with the monopoly selling rice, and other commodities, were the monopoly of printing books. At no point in history did we, as a society, conclude that if we limit reward producers it would add to the useful aggregate. That excuse was only invented after the "monopoly privilege" over copying books were renamed to "copy rights". At the same time that other monarchy monopolies were destroyed.
Society never discovered that it's worth in the aggregate. You cannot prove it's worth in the aggregate. Any attempt so far to measure the aggregate has been absurd. [2]
[1] http://en.wikipedia.org/wiki/History_of_copyright_law
[2] http://www.ted.com/talks/rob_reid_the_8_billion_ipod.html