Email at least you can set this up with a rule that checks the sender against your contacts and throws them into some folder.

True. I find setting up rules and adding to contacts adds work to my day-to-day though. I'm hoping to make something simple and seamless. Prefix inboxes are as simple as I could think so far: make one up, add a suffix on the spot when you handout an email address -- boom, locked to the first one who uses it.