At Regain Your Time, they discuss email etiquette and here’s what was suggested when using the cc..
Cc for CYA
Bad Idea: Maybe you’re not really sure if you’re on the right track, so you copy your boss, figuring that this will give her an opportunity to correct you if she doesn’t agree with your course of action. See above. She’s probably not reading it, and copying her does not absolve you of responsibility anyway. This is another source of communication breakdown within an organization, sometimes with damaging results.
Better: Run your intentions by your boss prior to the communication. Or, as above, address your boss directly in the message and invite her input. For example: “Jane, I think we should go with the 5×7 flier. Mary, please let me know if you disagree.”
And don’t even get me started on the bcc. And the bcc’in BS that occurs.