When we address an email we get to choose between "To", "CC", & "BCC."  Wouldn’t it be more worthwhile and call out more clearly what you are trying to accomplish by adding ‘CYA’ and ‘FYI’ fields?   

In all seriousness, during our work with customers on interpreting their email patterns we see scenarios where emails with more than 3 recipients are generally informational and not actionable (or viewed as such).  How do we know this?  These types of emails are rarely replied to indicating a one way push of information or FYI.  On the CYA front, blind carbon copies are good indicators of this type of communication as are looking at an organization’s hierarchy.  A subordinate including a supervisor (or even higher up) can be an indicator of someone covering their rear end, looking to project support, or even make a formal complaint. 

I imagine this was the logic behind former Morgan Stanley CFO Stephen Crawford asking to only receive email from certain senders vs. the entire corporate population.  Or as this story from InformationWeek highlights:

"(the) main issue is that he gets sent too many E-mails that put him in a disadvantaged regulatory position. He does not get to read most of it yet he has no deniability that he received it." 

Can’t say that I blame him if the very act of being included as a recipient makes me accountable for (and complicit in) the message content.