Yes - things like Twitter, IM group chats (FB/Hangouts/even IRC), all have a single "ring" of attention. A message is either to you, or to a group. There is no way for the sender to dial up/down the level of "attention" or send other signals when sending a message.

Some examples (admittedly, these are how they are used in my workplace and life, other people may perceive these differently, which is also interesting):

- BCC has an interesting side-effect of being able to drop somebody from the conversation, but notify them of that fact at the same time.

- CC is sometimes used as a "heads up". It means "I'm interested in you reading this, but I'm not asking you to do anything right now."

- To is explicit "I would like you to read this, and there's probably some action you need to do."

That said, these are used in my workplace so these rules don't really apply when sending more informal mails between family members and the like. I have tended to use CC at home when sending emails to teachers, keeping my spouse in the loop.

You can't really deliver the same messages within a Facebook conversation or a Google Chat. I think Twitter has some potential since the "to" line is fluid, but I treat the platform as read-only and find it extremely chaotic and unorganized.

> CC is sometimes used as a "heads up". It means "I'm interested in you reading this, but I'm not asking you to do anything right now."

It bothers me that Gmail combines the To and CC recipients into a single line. You have to do some investigating to figure out who's on To and who's on CC.

I think most of that dynamic was pretty common in paper memos. The only thing I see as plausibly novel is the "moving to Bcc" thing, where you politely drop participants from a Cc list.