Ballmer did not lay awake at night worrying about a framework primarily used for Linux desktop KDE applications. Can you think of one major piece of software available on Windows, Mac and Linux that was written with Qt? I don't mean an open-source project; I mean a piece of commercial software. Developers were not chomping at the bit ready to port their Windows software to the 2% worldwide desktop Linux market. Windows developers are using things like .NET, not Qt. The Mono project would probably be more of a worry for Ballmer than Qt.