I think this speaks to the whole idea of "Linux" being one thing. "Linux" is a technology, not an operating system. RedHat is an operating system. To say "Linux" is an operating system that should be compatible with every other "Linux" system is like saying "BSD" is an operating system that should be compatible with every other "BSD" system. When in fact this is not correct. There is no reason why Mac OS X should be compatible with FreeBSD even though they use the same Kernel. "BSD" is a technology used in OS X, but that doesn't mean that it should retain compatibility with anything else.

RedHat is an operating system. Mandrake is an operating system. SuSE is an operating system. Linux is not. The fact that you _can_ make an application run on all of these systems is an interesting side-effect of the fact that they use the same kernel. However, to think that this is absolutely necessary is silly.