Could offer some examples of "building upon" others' works which are not allowed without permission under current copyright law? I would like to understand what we as a society might be missing out on.
More generally, I become concerned when I hear "public interest" arguments because they usually apply a relatively static analysis of benefit rather than a dynamic economic model. It might be deemed in the public interest for pizza parlors to be forced by law to provide free pizzas. In the short term, we can imagine all the happiness these pizzas would provide. However, in the slightly longer term, it is obvious that there would be no pizza parlors at all. How does one show that limiting copyright would not have the longer-term effect of fewer works being created?