I have a very old private messaging system that either needs to be redone or removed. It currently accounts for about 20% of the activity on the site.
We already have a system in place for @mentioning users in status updates that works very much like Twitter. We also allow users to add a URL to their profile.
Should I remove the private messaging system? Are the @mentions and the URL sufficient? Or is it worth the time to rebuild it to maintain this functionality?