Microsoft Windows Vista NetIO
It struck me as odd that Microsoft decided to implement a new TCP/IP stack from scratch for Windows Vista. Yes, it does contain new features and the such, however, the new stack fell prey to something as lame as a land attack when it was released. Bloody heck. Why didn't they just import some legacy code, or most of it, then build upon it. That or at least have some decent QA before releasing the new stack. Microsoft deserves kudos for recent efforts, however, they need to put more into QA, and less thought to market forces.