It's basically equivalent to "you should sign up for my email newsletter" but without the classical email problems of being unable to unsubscribe from the list, or your address potentially being sold to third-parties. (Also without a permanent "inbox", so people will miss what you say if they don't check right at the time--but that also means that you'll never end up buried under all the other stuff people haven't checked, so I imagine that evens out.)
