Your crypto-enthusiast friends will be like "why is our conversation CC'ed to another number?" and you'll have to explain to every single one of them that it is

Your crypto-enthusiast friends will be like "why is our conversation CC'ed to another number?" and you'll have to explain to every single one of them that it is a multi-device workaround. And then when the NSA decided that they need their number CC'ed, your friends won't ask you...