The reason it matters what the name is, is that pkg_resources can't otherwise
detect that it's being imported from an egg.  We could drop this mode of
installation altogether in 0.7, but it's here to stay for 0.6.  (Changing
priority to "wish".)

If you follow the install instructions on
http://pypi.python.org/pypi/setuptools/0.6c9#cygwin-mac-os-x-linux-other with
Safari on Mac OS X, you will probably accidentally rename the egg to
setuptools-0.6c9-py2.5.egg.sh, since Safari does that for you automatically
without really pointing out what it is doing.

Then if you run it, it will say "./setuptools-0.6c9-py2.5.egg.sh is not the
correct name for this egg file.  Please rename it back to
setuptools-0.6c9-py2.5.egg and try again.".

Why does it matter what the name is?

I ask because I don't want to advise my Macintosh users to follow the
instructions at
http://pypi.python.org/pypi/setuptools/0.6c9#cygwin-mac-os-x-linux-other if it
is going to lead to these sorts of issues for them, and nor do I want to explain
to them how to download a file without letting Safari rename it.