No Place Like Home

Currently, Sony's Play Station Home is the only console-based virtual world.  I would think this is a space that Microsoft would be interested in:  (Virtual Worlds News)

Home features 100 games, an average user session time of 70 minutes, over 50 virtual spaces, 85% repeat users, and 14 million users overall.

That's pretty good.  That 70 minute session time alone would suggest that this is a space that the ad world should be interested in. For that matter, why isn't there interest in the PSP side of Sony to provide a mobile experience?

For that matter, at the point you're providing 100 games I would think someone would create a mobile device whose only function was accessing that virtual space.