Your 4 step instructions have doodle@, but the actual mailto: is for wb@. It's a minor thing, but you should be consistent.
Cool idea. I think you could run pretty far with a posterous style lazy signup and more options (like the dropbox idea, some storage, etc.) Maybe support group emails, so dev@ when sent from my email address returns a response to a certain 5 people.
I have no idea how important blackboard is - probably less so for the business world, but plenty of students use/encounter them.
If it's easy to work out a algorithm that cleans up the blackboard but harder to work out detecting the blackboard, your idea of two email addresses (doodle/wb@, and blackboard/bb@) would probably be a good solution.