Sadly, I am typing this message to you folks on a Rev B Aluminum Powerbook G4 with slight corrosion on it....
I bought my Powerbook about a year and a half ago, and the corrosion just started showing up about a month ago... needless to say I am very disturbed by it...
The corrosion on mine is only on the left wrist-rest area, which is directly above where the hard drive is. Since the computer gets a bit warm, my left hand always sweats...which I guess has caused this whole problem...
-S