http://exophase.com/23731/rumor-gear...-by-microsoft/

Microsoft (or a company in the employ of MS) apparently leaked it by posting the code on one of their own dev sites, fully accessible by the public. Oops.

This one doesn't smell of viral marketing to me, like when MS "accidentally" made Fable 2 free on xbox.com a week before Fable 3's release. This appears to just be a colossal screw up. So can MS sue themselves? ;-)