I bet Google would *like* to penalize a noarchive tag, but because of the copyright-morass that they are in with the whole archiving feature, they probably think that would just add salt to the open wound.
Right now they can argue, "Any site that is really opposed to the cache can disable it easily." If they penalized the no-cachers that whole argument would be easily deflated.
No cache has nothing to do with cloaking - it has to do with with copyright. I've looked and looked for no cache cloakers, and I can only find a handfull. I still think it hurts your rankings, but I'm going to use it anyway.