I've posted to python-dev about this:

http://mail.python.org/pipermail/python-dev/2013-February/124114.html

At the very least the pickle docs deserve some mention of the behavior.  That way people won't need to spend as much time trying to figure out why things aren't working the way they expect.

However, my preference is to fix pickle, though I readily concede that might not be possible.  And just to reiterate, I agree we shouldn't do anything here without a clear picture of the impact.