In reply to Si dH:
> Not noticed discolouration but will have a look. Difficult to know what it would imply too.
I'll snap a photo later Si and try and show what I mean.
> Your point about helmet type is a fair one, but I used to do more winter and alpine stuff, and still wouldnt want to buy something unsuitable for those activities.
Yep, its a very fair point. I guess we shouldn't use the word "unsuitable" in either direction (loads of guides and totally hardcore ice climbers use Meteors or example, and the Armour is perfectly OK helmet for rock climbing), but perhaps just that some are more suited to minimise certain risks than others.
I was reading Jon Griffith's blog again recently look at the amazing pics of him and Will Simms climbing in the Karakorum, both with foam helmets. I guess its a very fair argument that the lighter you are, the faster you go, the safer you are and hence that's an acceptable trade off.
If nothing else I hope the article has given people some food for thought and just gives them some more info to make their own 'informed decision' from next time they think about buying a helmet.