Antoine: I agree programmers shouldn't try to create situations like this.

Consider however an application assembled using a build tool like
zc.buildout, which installs each package into a separate installation
location (based on setuptools and easy_install).  If the application
uses several packages from the "foo" namespace (to keep with the
original names from the report), there will be directories matching the
first and third packages from the example.

Now, further development on the application may cause a 3rd-party
package named Foo to be used.  This name is not the application
programmer's to select, and the volume of code from the "foo" namespace
may be too large to modify; it may represent 3rd party code (for
example, the "zope" namespace package contains many widely used
examples; if used at all, many are likely to be used).

So I think the original use case stands, and may even be more important
than ever given the widespread use of "namespace" packages.

This also suggests that developers should check for the existence of
packages of similar name before releasing code, in order to avoid this
situation.

(I'm disassociating msg20510, since roundup doesn't screw up the tree in
the original report, so that message no longer adds anything useful.)