Well, Andy R if you have an accident and you were attempting to land in a crosswind outside the aircraft's demonstrated limits then you are in a sticky situation nonetheless. If you injure anyone and you find yourself getting sued - it is going to be tough to defend your actions in such a situation. The "....well I know it is technically outside the limits but everybody does it" defence isn't a strong one.
You're right that is is a DEMONSTRATED crosswind, but even though it may not be limiting it doesn't automatically guarantee that the aeroplane CAN operate in stronger crosswinds. Sure, with common types like Cessnas, there will be plenty of people who will say they have operated the equipment in stronger crosswinds than the POH states but once you are outside the limits in the book you're going to have to explain why.