Being an engineer, I look at this from an engineering perspective, and I have to say that the comments quoted below are extraordinarily disingenuous. When you design a product, you design it for its expected use, and make sure that it is robust for that use. The designer doesn't get to choose what that use is; the customer does. If the designer can't meet the customer's requirements, he shouldn't design and market the product, or should find some way to restrict it to the use for which it was designed. To try to limit how their products can be used, while making no effort to restrict sales to "proper" users, is really pretty lame.
Bicycle components are consumer products. As such, they have to be designed to withstand a certain amount of abuse. How much, of course, is open to discussion; for example, cracks in a 30-year-old crank probably should be expected, but cracks in a 5-year-old one, even if subjected to heavy use, probably aren't acceptable.
This idea is fundamental to all of engineering: things work because they are robust, not because they simply do what they were designed to do. If you don't buy this, contemplate the case of an airplane whose wings break off in severe tubulence, and the manufacturer claims it's not his fault--the plane wasn't designed to withstand heavy weather. It's the pilot's fault for flying into the turbulence.
End of sermon.
> Richard adamantly says that Campy cranks are built solely for racing and
> should be considered to have a limited life. Therefore, use of Campy Road
> equipment for Mountain bike or BMX use violates the Campagnolo warranty and
> safety recommendations. These cranksets are often subjected to many many
> miles of continued stressful use on the crankarms where racing/Mountain/BMX
> heavy riding sometimes causes the crankarms and/or pedals to crack when
> there is a bike crash, or for no reason at all.