a bit more rationale for absolute imports

pep-0328.txt

@@ -83,7 +83,10 @@ package, it is not clear whether ::
     import foo
 
 refers to a top-level module or to another module inside the package.
-To resolve the ambiguity, it is proposed that ``foo`` will always be a
+Let's say today it refers to a module internal to the package.  Then
+tomorrow, the standard library decides to add its own foo package that
+you'd like to use.  You can't without renaming your internal module.
+To resolve these ambiguities, it is proposed that ``foo`` will always be a
 module or package reachable from ``sys.path``.
 
 Because this represents a change in semantics, absolute imports will