I don't own a disc-brake bike so I have absolutely no experience on this front, but the talk about contamination is interesting.. Isn't it normal in the course of road riding, especially in slightly wet conditions, for all manner of road spray that's contaminated with who knows what (oils, salt, etc..), to get everywhere (including disc pads)? It just strikes me odd that there's concern on what can and can't get on the pads.