A Minor Quibble

In baseball terminology, obstruction is a term used to denote a violation committed by the defense, while interference is called when the offensive team, a fan, or even an umpire interferes with the play. However, a violation committed by the catcher, whereby he makes contact with the batter or his equipment during his swing, is called catcher's interference. 

Due to the use of the terms "interference" and "obstruction" in the official baseball rules, denoting obstruction as done by the defense, I think this violation would more rightly be called catcher's obstruction. However, due to its constant reference as catcher's interference, a term which has permeated every baseball player's vocabulary, I am not suggesting that we change the term, but merely look at it a different way. 

It's really annoying when you forget the difference between interference and obstruction, and for what it's worth, using catcher's interference as your memory tool is not ideal.