cams-good or bad?

okay, may be a stupid question, but are cams bad for the engine. it seems to me that something that pushes your pistons down faster and harder would cause more friction, more heat, more problems with the pistons in general (cams push down the pistons right?, if not my whole argument is null and void). i've never heard of a car being messed up because it had aftermarket cams, but i was wondering if this could happen.

A camshaft pushes down on the valves. One of the main reasons that cams are upgradable is because auto manufacturers strike a balance between idle properties, emissions, and power.

Aftermarket cams tend to try and get different degrees of power. Idle quality is usually effected and emissions usually always goes down to some degree.