KIlt pins are a "newer" part of the kilt. The story is that Queen Victoria was walking by a Highland Regiment on parade (formal thing, not through streets), when a gust of wind blew open a kilt, revealing what was beneath. While others were embarassed, she simply removed a hair pin and inserted it in the kilt to hold it down. Some regiments use a hat pin as their kilt pin in memory of this, though it is simply decoration.

A kilt pin is largely extra decoration of the outer apron, as virtually all are useless as a "wind deterant." They do allow the wearer to show more personality, as if the kilt itself was not enough. Some get heavier pins, so it seems more funtional. The problem is that if it is actually heavy enough to do much good, it affects the hang of the kilt. A danger is that a kilt pin may damage the kilt itself, by making a small hole or twoin the material itself, either by snagging something or the weight pull for a heavy kilt pin (especially on a lighter weight fabric). Therefore, many do not use them at all. But, a kilt pin is a good way of displaying personality or provide a good excuse for a man to wear jewlery that he would normally shy away from.

Myself, if I wear a kilt casually, I do NOT wear a kiltpin,but I do if worn in a more formal environment (where suits, coat and tie or nicer, are required).