Index: authentication.txt
===================================================================
--- authentication.txt	(revision 6784)
+++ authentication.txt	(working copy)
@@ -315,10 +315,16 @@
     else:
         print "Your username and password were incorrect."
 
+
+Note that a side-effect of a successful call to ``authenticate()`` will result 
+in the ``User`` object being annotated with the appropriate authentication 
+backend (see `Specifying authentication backends`_). 
+
 To log a user in, in a view, use ``login()``. It takes an ``HttpRequest``
-object and a ``User`` object. ``login()`` saves the user's ID in the session,
-using Django's session framework, so, as mentioned above, you'll need to make
-sure to have the session middleware installed.
+object and a ``User`` object, where the ``User`` object must already be 
+authenticated. ``login()`` saves the user's ID in the session, using Django's 
+session framework, so, as mentioned above, you'll need to make sure to have the 
+session middleware installed. 
 
 This example shows how you might use both ``authenticate()`` and ``login()``::