"Authentication is more important than encryption.  [snip] Imagine a situation where Alice and Bob are using a secure communications channel to exchange data. Consider how much damage an eavesdropper could do if she could read all the traffic. Then think about how much damage Eve could do if she could modify the data being exchanged. In most situations, modifying data is a devastating attack, and does far more damage than merely reading it." [Bruce Schneier]

To me, validity of an assertion is as important as authentication.  Authentication has little value if the database is filled with invalid information.  It doesn't take much expertise to write a script that creates a million Hotmail accounts using randomly generated registration information, filling Hotmail user database with trash.  I can be Jack Frost living in Alaska or Don Juan living in Spain.  Garbage in, garbage out.  Authentication just means restricted access to garbage.