Why do Microsoft move buttons to the right?

I just installed Internet Explorer 7. It looks nice, but what on earth did Microsoft think when they moved some of the toolbar buttons to the right? Did they completely miss out on the idea that people stack windows, rendering the buttons invisible when a window partially overlap?

I can understand that not everyone reads from left to right, and therefore would like buttons to display to the right rather than left. But why distribute them all over the place?

I just don't get it...