From the blog post entitled Spaces and Messenger integration added on the Windows Live Mail team's blog, Steve Kafka lets us know

I just blogged about this on my own Space and someone asked why it wasn't mentioned here on the team blog. Because I forgot, that's why.

We just added the "contact control" to contacts in Windows Live Mail. If you frequent Spaces, this will be familiar to you. For contacts that are Messenger enabled this lets you see their profile picture, Messenger presence, gleams (the "something is new" indicator), their contact card and more. Check out my original post for a screen shot. To see it for yourself, go to your contacts and click on some of your friends from Messenger.

We're definitely working on more integration between Messenger, Spaces and Mail, so consider this just the beginning.

The contact information which is used for the contact control is another one of those core services our team provides as platform piece for other Windows Live user experiences like Spaces, Messenger and Mail. Eventually I'd love to see the contact control integrated across all Windows Live experiences where users have to be identified. It's much better than just a username, dont you think? In the meantime you can check out my screenshot of the new integration in action.