Well, some people already give friends and family, at least, a different email address entirely. ("Personal email" vs. "work email".) The system as described seems more useful for the "work" version.
Then again, it doesn't fully accommodate the way I use my work email, personally. I'm on a number of mailing lists at work where I don't personally respond to most of the email --- but I read a lot of them anyway, in part to keep abreast of what's going on, and in part to be able to exercise my own judgment about whether I should jump in. That's an awkward fit for a workflow that assumes that every email calls for some kind of response.
Then again, it doesn't fully accommodate the way I use my work email, personally. I'm on a number of mailing lists at work where I don't personally respond to most of the email --- but I read a lot of them anyway, in part to keep abreast of what's going on, and in part to be able to exercise my own judgment about whether I should jump in. That's an awkward fit for a workflow that assumes that every email calls for some kind of response.