Last week, NBC postponed the new episode of The West Wing that was to air Wednesday night, presumably because of the ongoing baseball playoffs (both the NLCS and ALCS had gone to sixth and seventh games, and both series involved a long-suffering franchise). Via The Modulator, I see that another theory for the pre-emption, which involves the episode's North Korea-related plotline. (The episode is now supposed to air tonight.)
I doubt that's the case, though, because NBC also put reruns in place of its Thursday night schedule the same week (up against ALCS Game Seven), and CBS likewise postponed a new episode of CSI Thursday night. (I don't watch anything on ABC, so I have no idea if they had to similarly postpone new episodes that week.)
I was surprised that the networks had anything new scheduled at all last week, but maybe they simply assumed that baseball's playoff ratings would continue to be less than the bonanza they used to be, only to be caught unawares by the drama of watching the Cubs and Red Sox come oh, so close.