I posted a picture on a bodybuilding site, whilst I was using melanotan II and someone commented on my white spots and said that I had tinea versicolor
(
http://en.wikipedia.org/wiki/Tinea_versicolor)
I read up about it and, as stated in the wikipedia article, 2% to 8% of people "suffer" from it. I would suggest the white spots that people are referring to are quite likely to be of this cause. Many of you would not have noticed it before due to pale skin and those with ongoing exposure to warmer environment (ie. most of us are doing this in summer), are more likely to have issues with it.
I just went down to the pharmacist and they gave me some cream (same stuff used for athlete's foot). It's basically just a skin infection that will go away with consistent applications. Mine started to fade when I was using the cream but then summer went and I became pale again and didn't bother with continued application because they were barely noticeable again.
Anyway, people may be referring to something quite different but hopefully that will help someone out.