Nick writes, "It's an interesting decision coming from a Supreme Court that recently ruled in favor of the big guys in Eldred v. Ashcroft, which OK'ed massive extensions in copyright terms. There may be no consistent judicial philosophy at work here, but at least this new ruling expands expression."
I don't think there's an inconsistency here, though I would have preferred the court to rule differently in Eldred myself. The key issue in Eldred was whether Congress has the right to extend copyright terms indefinitely, not how powerful the extended copyright protection should be. The new ruling, on the other hand, deals with the proper interpretation of the law—on how much dilution constitutes "harm"—and not with the existence of the law itself.
Also, since this case involves trademarks instead of copyrights, there's a different set of constitutional issues at play. Trademarks do not exist "To promote the Progress of Science and useful Arts, by securing for limited Times to Authors and Inventors the exclusive Right to their respective Writings and Discoveries." They're just there to prevent customer confusion—in theory, anyway.