Ajax as the iPhone SDK

As anyone who has written apps for phones will tell you, it is big ole pain in the ass and you often have to use a bunch of proprietary software and hope that they work on all kinds of different models of phone and then you'll likely have to do it again for when you want to support another brand of phone. Using Ajax means you've already got a bunch of developers who already know the environment, the language and platform.
It was also a good excuse to port Safari to Windows and has the following bonus reasons.

• iTunes IS the music app, they will get some "halo effect users" and Windows kids can now pretend to be cool like their Mac friends


• Windows shops can now test their site for Safari compatibility and not have to have a Mac laying around


• Send a big fuck you to Microsoft who gave up support of IE for Mac not too long ago

I think it was a pretty damn good idea.