[Jim S]

Well as one who has been around a while not only have I seen this called several times, I have called it myself once.
The use is for a foul that is basically an unfair or dangerous act. Such as: the receiver has beaten the defender who then tackles him from behind simply to stop the receiver from any chance of catching the ball. Or, as stated, above the player fouling does so in what is a personal foul.
The enforcement we were given these many years ago was to enforce the PI and then the intenional part as an unsportsmanlike conduct. No question of a multiple foul.
It's too bad this is not called more.
The rule is there. The purpose for the rule is there. The mentallity that we shouldn't call it because "the pass interference rules are tough enough already" starts to put personal opinion into the enforcement of the rules. Perhaps if this were called once in a while there would be fewer plays on which it should be called.