Bobby pointed out that there was certainly nothing in the rules of golf prohibiting practice swings, but I suspect he would not have objected to such a rule. While confirming a player's legal right to take as many practice swings as he likes, Bobby writes: "While thus defining the player's legal rights, it is only fair to say that his moral right to make a nuisance of himself is not so clear. It is probably natural that a man playing golf is interested in nothing so much as his own game. It is also natural that he should attend to his opponent's game only enough to hope that said opponent will encounter enough trouble to cause him to lose the hole. But if he feels this way, he ought to remember that his companion probably entertains some such notions of his own play, and that he certainly has not come out to spend the greater part of his afternoon watching someone else take practice swings and fiddle around over a golf ball in making preparations to strike it. The ethics of the game allow each person a reasonable opportunity to play each shot carefully, but they demand also that the player step up promptly to do his bit without unnecessary delay."
Bobby goes on to talk about the habitual practice swingers and their "uncanny talent for taking their swings at precisely the wrong times." Bobby writes: "Everyone has had the experience and knows how annoying it is hearing the swish of a club behind him just as he is in the midst of his swing. He has to be very fond of the culprit to restrain a desire to bash him on the head with the club, even when he knows that the guilt is only of thoughtlessness."
Many teachers extol the virtue of taking practice swings as part of preparing to hit a shot. The only problem, in my mind, with this recommendation is that most average players have a practice swing that bears little or no resemblance to the swing they make when it counts, when there's a ball to hit. That being the case, it becomes hard to argue that there is much virtue in the practice swing if it can't be copied when it comes time to actually hit the ball.
Bobby once told the story of playing golf with his father, who, after hitting a particularly poor tee shot, took a practice swing, turned to Bobby and asked, "What's wrong with that swing?" Bobby replied,"Nothing. Why don't you use it sometime?"
In conclusion, if you are one who prefers to take practice swings, that is certainly your right. But, please, for the sake of the game, the pace of play, and the sanity of your playing companions, take your swings judiciously. The game is hard enough as it is.