In reply to JimboWizbo:
Historically, Bleusard ethics have been pretty firm that chalk is evil and will destroy the rock whereas pof is all good.
The official line doesn't seem to have changed, but these days chalk is pretty common - and not just among young folks who don't get the ethics, Bleusard legends like Jo Montchausse seem to be happy using it in moderation, too.
Personally I might go for a quick dab of chalk if I keep greasing off a particular problem, but avoid just slathering it on by default. I have yet to be shouted at. I also don't go to font in high summer, though...