From what we've heard about the development process of Windows Phone 7, rumors about the OS predated its earliest seeds. How? The secret lies deep underground in Redmond, buried with a little project called Photon.
We were posting about Windows Mobile 7 (and 8!) in great detail back in 2008, and we weren't the only ones. For months prior and years after, Windows Mobile 7 leaked screenshots were a reliable fixture in tech news. So there was clearly something there.