“What is the expectation?” is such an important question that never gets asked. This used to be pretty simple when communication channels were basically just a call, e-mail, fax, or a letter. But, with a whole bunch of other channels added to the mix, most of us just assume everyone else uses all of them the same way (How often do you check your e-mail? Is your cell on silent all day? What does it really mean when your Skype status is on do not disturb?) and imply the expectation based on that assumption whenever we send any type of message. And even if we have an idea of how a certain recipient uses their communication channels/tools today, it might all be different tomorrow (new smartphone, changed notification settings, finally downloaded xyz app).
Glad to see some very smart people are thinking about this as well.