>Why is it that it's OK for a business to ignore Linux and Mac users ... but it's not OK for a busines to ignore the same fraction of Windows users?
I don't think it's "OK" as much as it is a business decision. Developing software for various platforms is vastly different (in terms of resources) than developing websites for cross browser compatibility. The barrier to entry in the web world is also much lower, which leads to a higher level of competition and as I mentioned if you don't support a browser, a competitor will. As you no doubt know, that same statement isn't commonly made about platform software.
I don't think it's "OK" as much as it is a business decision. Developing software for various platforms is vastly different (in terms of resources) than developing websites for cross browser compatibility. The barrier to entry in the web world is also much lower, which leads to a higher level of competition and as I mentioned if you don't support a browser, a competitor will. As you no doubt know, that same statement isn't commonly made about platform software.