Editorials are, as a rule, unsigned. That's what makes them editorials as opposed to op-eds or columns. They represent, ostensibly, the opinion of the newspaper itself rather than any individual staffer. The NY Times does the same thing.
(The WSJ could avoid a lot of confusion if it labeled its editorials "Editorial." Instead it labels them "Review & Outlook," a term only regular readers of the opinion section will be familiar with.)
