[msc]

They did something similar last year. Edit: http://blogoscoped.com/archive/2008-10-31-n76.html

[mcxx]

And how did someone discover that?

[ks]

My guess is that it was "leaked" by someone working at Google.

[tlrobinson]

It wouldn't surprise me if there are SEO people watching Google's every move for hints of changes in Google search. Though I'm not sure how robots.txt would apply.

[derefr]

More likely than SEOs, bloggers are probably looking for any new hint of an as-of-yet publically-invisible service, so they can be the one to start the rumor.