I have been building custom office automation software for some little time, and the reality is that any new system is always trying to wean people off managing all their communication and process by email.
Even as we speak I am building something for a client and we are taking the view that writing things on "walls" and commenting on "stories" just like Facebook as some potential for diverting information from email into the app. We don't know if we're right, but that's how we're betting.
We could simply tell people to use our app for everything, but my experience is that if whatever you build is dictated by managers in the hopes of straightjacketing people into some new process, they will route around it using email as a back-channel.
To beat this, you have to be better than email in some way that the users themselves appreciate.