For networkability in the class of Windows, it is true. Windows is a monopoly product, and Microsoft has done everything possible to make sure that noone will be able to compete with the same caliber (scope of networkability) of OS. Ironically, I think one of the worst situations is the fact that MS owns and controls DirectX. What a gigantic conlict of interest that hostage code represents while in MS' hands. It's not just a problem for gamers, though it is one for them, but I think it all but guarantees that advancements in graphics will have to come from MS of all places. This is a horrible thought for me. Only a lawsuit will wrestle control of DX from MS.
The other really horrible situation is the complete dominance of .NET when it comes to development platforms. This is another area where MS has vehemently controlled the marketplace by setting up everything so that it's easy to develop for Windows and by making sure that the developments for Windows aren't 100% easily adaptable to other plaforms.
Linux competes with Windows with the scalability and better than Macs do. Apple is too concerned with keeping their own identity and maintaining loyalty to their product line amongst customers. They don't care about networkability as much as MS do. The problem for Linux is that it's not as simple to develop for the platform, and also it's an entirely new platform to learn. None of the language of the OS is common to Windows. There isn't any money in developing for Linux, so who can afford to devote their life to the platform. Thank goodness it's there and thanks to those who have worked on it, but it's not easy competing with Windows while not being able to use the exact same language references for elements of the OS when speaking to potential users.
When MS bought DOS, this whole sequence of falling dominos began. I feel like we kind of have ourselves to blame for letting it get to this point in a way...