I went out for a the day on Saturday and when I came back I went up to my room to check on how my Macbook was doing with copying some files into iTunes when I noticed that the charger indicator on my Magsafe was orange, meaning charging. It had been plugged in overnight and was green, meaning finished charging, since I left. So it was strange that the laptop was charging rather than just running off the mains power. I then went to move my Macbook when I noticed a few sparks and some smoke and to my horror I looked down and noticed that where the thin cord comes out of the power brick, the wire was burnt and was smouldering! Obviously I very quickly unplugged it and held it well away from anything flammable as clearly the thing was still extremely hot. Needless to say I took it into the Apple store today and got a replacement instantly (brilliant service as ever Apple!), but not before snapping a few photos to show everyone: