I've no idea why. I didn't change anything in the settings. I almost don't mind it either way -- except that I do slightly prefer having the trackpad locked out -- but it's not a big deal now. I know that some people feel different about that. I've no idea what caused the change. I just thought it was strange and funny that mouse movement is suddenly waking up my MacBook, and that I would share this earth-shattering piece of information with all [un]concerned. Edit: I can actually think of one thing: I installed and started using BetterTouchTools. I didn't assign any gestures that had anything to do with waking up a Mac though. I also can't say for sure if this started just after or a few days after I installed BTT, or if it has anything to do with it.