  We test the claim by Yu et al. -- presented in Science 322, 104 (2008) --
that the degree distribution of the yeast (Saccharomyces cerevisiae)
protein-interaction network is best approximated by a power law. Yu et al.
consider three versions of this network. In all three cases, however, we find
the most likely power-law model of the data is distinct from and incompatible
with the one given by Yu et al. Only one network admits good statistical
support for any power law, and in that case, the power law explains only the
distribution of the upper 10% of node degrees. These results imply that there
is considerably more structure present in the yeast interactome than suggested
by Yu et al., and that these networks should probably not be called "scale
free."
