well to me - if I am CC'ed in conversation it means as FYI or "I'd like to hear your opinion", "I hope you don't mind" or similar, i.e. I am on CC just to stay

well to me - if I am CC'ed in conversation it means as FYI or "I'd like to hear your opinion", "I hope you don't mind" or similar, i.e. I am on CC just to stay informed, not to actively be on conversation, also sometimes informs the receiver that this is known to someone else. Other case when 2+ parties with several participants in each are agreeing on something/negotiating it resembles semantic conversation much better you send email with TO set to other parties (you say them this) and CC your colleagues (they hear this and stay in conversation). Btw, and I don't like when people don't include all recieptients when replying, Gmail somehow promotes this