Well, I just noticed this. I've had my macbook for 2 years and have never had an issue. I'm sitting here and I turned off my music and I heard a buzzing/vibrating sound. I moved around til I heard it and it's coming from the macbook charger! Like the default square piece. It's fairly quiet but I would have noticed it before...kinda sounds like an aquarium pump. Anyone else experienced this? I'm not that worried, but I don't my charger to mess up and like fry my battery or catch on fire (unlikely IMO but just saying). Oh, and it gets slightly louder when I scroll on the trackpad. WTF. And no, I'm not imagining this. also my battery has 1 green flashing light on the bottom and my battery is at 28% and says it's charging.