The other real question is: why? Apple could merely be sending ideas out there to see how they'll play -- the WSJ post specifically mentioned a 10 or 11" display, so it's possible they wanted to pre-test that idea. Martellaro also reckons that Apple's message could have been directed at another company, either a competitor or a partner who needed to be reminded that the tablet release was approaching quickly. And finally, it could have been directed at us press -- rumors build more rumors, which build hype, which, as Martellaro says, put butts in seats at the event later this month.
Of course, there's always the question of stock manipulation, and it could be argued that leaks like this might cause problems there. But otherwise, leaks by Apple are more or less harmless to everyone besides the company itself. If Apple did leak something it doesn't end up delivering on (i.e. promises of one product and another one ends up getting released), it's the companys own reputation that will be on the line. Apple can say that it doesn't respond to or support rumors, but when the company's own executives are allegedly telling the WSJ what the tablet is like, the onus falls on the company's reputation as a whole.
[via Apple Insider]