Looks like my 1.5GHz 15″ Aluminium PowerBook (bought in April ’04) isn’t the only one to suffer from weird “pitting” and other surface damage see: http://saladwithsteve.com/osx/2004/10/powerbook-pitting.html.
I’m about to buy an extended AppleCare contract and see if I can get Apple to repair it and other issues.