Cory Doctorow posted on Boing Boing the other day about WoW's EULA being unreadable when installing the game on Linux. And obviously he's right -- Linux doesn't always have the font that Blizzard's installer uses, and so when you try to run it on Linux, you get gibberish, at least during installation. But there's more to this story here -- running WoW on Linux is actually unsupported by Blizzard: you can do it, and it's not against the EULA or ToS (in fact, Blizzard actually worked with the WINE guys to make sure the game ran correctly), but obviously any issues you have are an "at your own risk" kind of situation. So Doctorow's pretty much out of luck (or in luck as the case may be -- it's unlikely a EULA could be enforced on an unsupported system).
And Linux isn't the only unsupported major OS out there -- Microsoft will release the beta of Windows 7, the new version of Windows, into the wild on January 10th, and Blizzard has made it clear that they won't support that, either, at least until it gets out of beta and into a release state. Of course, Microsoft has an interest in making sure old versions of Windows software work with the new OS, but if you only have one computer and absolutely need to play WoW on it, you should stay away from Windows 7 until the bugs are ironed out.
Then again, there are worse OSes to deal with.