This is tangential, but I drive two of my favourite web apps almost entirely through email (Tripit and Highrise) and a third (Instapaper) quite a bit. I basically live in Instapaper and Highrise, so that's saying something.
I have email literally everywhere and email reminders are still easily the most effective notification system for a bunch of things I've seen.
I have email literally everywhere and email reminders are still easily the most effective notification system for a bunch of things I've seen.