And if installed properly, there is minimum friction using a spring - you need to shim between the spring and rocker and should always shim between the rocker and hold-down.

Some have mentioned the rocker moving sideways enough that the rocker tip moves off the valvestem. I'm not saying it can't happen BUT what heads have that wide of a pushrod hole that will allow the pushrod that much movement? Stockers don't and neither do my Indy EZ's. Just sayin'!