"[T]he conclusion that a greater numbers of works will be created when there are greater monopolies fails to account for the negative implications of broad monopolies on creative expression. When the scope of the copyright monopoly becomes too great, the creation of new works is, itself, hampered. After all, each creator of a new work builds in some way on the works of the past. With overly broad monopolies, new works that build upon old are not created, creativity is stifled, and thus the net value to society is lessened. We have, what Judge Walker referred to a 'monopolistic stagnation.'"