One of the features I really want on PokerDIY is the ability to use Private Messages instead of email (or both) whenever a notifcation is sent via email. The user could then set their preferences if they want to use emails, PMs only, or both. This makes the portal much more message-centric, which allows greater collaboration and less reliance on email infrastructure. It also encourages "stickyness" and encourages users to return to the site.
So when a user makes a Wall post, invites you to a group, sends you an event invite or friend request, you can queue it into the PM system.
I can do this quite easily in the Smart-Thinker modules via integration with the Ventrian Private Messages module, except that we need a public interface on the Ventrian module that my modules can call on certain actions. I think it is a fairly small bit of work to allow this on their side, and it will provide massive benefit. Of course Scott from Ventrian probably has as little time as do, so I completely understand if he is too busy to do it, however if you would like to see this type of functionality please head over to Ventrian and add your support, and perhaps in the future we'll see this feature.