Promoting conversations to more heavyweight communication mediums

There's all these different communication mediums -- IM, twitter, email, wave etc -- each of which have their own place because they have different affordances making them suited to different sorts of purposes.

But I wonder whether we can have better integration between them.

One dimension on which these mediums differ is their 'weight' - Twitter is quite lightweight, wheras email is more heavyweight, and wave appears to be weightier still.

Sometimes it would be useful to 'promote' a conversation from a lighterweight medium to a heavierweight one. What might start out as a twitter conversation might end up being better served by a wave.

Perhaps communication tools could support this conversation 'promotion'. For example, by supporting a full history of the conversation, spanning any changes in medium. The tools could also have knowledge of peoples' different identities across the different mediums, so that if you went from an email to certain recipients to a wave, all those people could be automatically added to the wave.

(and along with the notion of 'promoting' conversations, you could also have the inverse - demoting conversations).