"Show me just what Mohammed brought that was new, and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached." - Manuel II Palelologus
Agreed. I don't think Apple will crack down on the little guys and little sites hacking OS X to run on non-Apple hardware; the more people use a sort-of, kind-of Mac, the more interested they're likely to become in a no-compromises version. At least that's true of hobbyists who go in with both eyes open and know that they're applying a kludge and can expect no support.
Folks buying a turnkey Mac "clone," on the other hand, are more likely to think that it's actually a Mac, and when it isn't stable or upgradeable, more likely to be turned off by the Mac altogether.
All that aside, I know that in some areas of intellectual property, you can lose your IP rights if you don't make a good faith effort to enforce them. I don't know if the courts have ever applied that to a EULA, but it's possible that failing to enforce it here would be a first step to it being considered unenforceable later.