I wished Microsoft would have first solved email spamming, but kittenish as they are they first provide a global platform where PC and Xbox gamers can play together and be able to manage one single gamertag across those platforms.

Gamers will have the ability to access Xbox Live world from their Windows-based PCs early next year to play games with friends. The Xbox Live experience on Windows will give gamers a consistent online game experience in which they have one identity, one friends list, one set of achievements and voice communications across all games on the network.
Of course this will only be available with the launch of Windows Vista.
Microsoft will also provide mobile access via Windows smart phones next year to the Live Anywhere platform.
This gaming infrastructure is hard to beat. Sony's online network will have a hard time to compete with this. Currently more than 3 million console gamers are connected to the Xbox Live community via their Xbox and Xbox 360 consoles and Microsoft expects that number to double to 6 million by this time next year. In addition, more than 25 million casual gamers are currently playing games on MSN Messenger and MSN Games.
More details on the xbox.com site.