Microsoft owns the desktop - that's their cash cow. For large businesses they (basically) have to buy outlook / exchange. They throw powerpoint, visio, word, excel on top of that, plus the operating system, and they own it. From an operating system standpoint, there's not any real threat. From a productivity suites perspective, there's a bit more threat from cloud, but it's still comparatively small. Same can be said for email - gmail is a much larger threat but for corporate security, calendaring, integration, it's still not really there. This will probably be different in 5 years as the proprietary protocols and integrations move towards open standards. I find it ridiculous that I can't find another desktop email client that will natively work with exchange/MAPI, and Microsoft knows it. Skype is just extending it to the desktop, and it's a strong part of the desktop suite. I think they want to play in the enterprise space, because nobody wants to use Lync for anything other than IM (aforementioned turd comment here).