Looks like some people are not really able to keep up with secrets when it comes to Microsoft betas, a Windows beta tester has posted the attached screenshot from the upcoming Microsoft Beta for Windows Centro.
Telling by the post at Neowin and some other sources, it seems that MS has started sending invitations out for those willing to test Centro and it appears that the first build is already available for some of the lucky testers who were invited to this beta.
News Sources: Neowin and ZDNet