Apple bobbing has long been associated with Halloween as an activity kids/adults do at parties. The activity originated with the ancient Celts and involved placing apples in a large basin of water. Apples, being less dense than water, would float freely around the basin. Each person in turn would hold his/her hands behind his/her back and try to pick up an apple with his/her teeth. Traditionally, the first person who managed to remove an apple from the water was to be the next person to marry.
This activity seems silly now, but like all other gatherings at that time, these served to bring people living in remote regions together who may not have met (or married or produced children). These get-togethers helped keep the population going and surely allowed news to spread.
I would think this activity will slowly fade into Halloween history. I can't imagine dipping my face into a bucket of water that other people have also dipped their faces into before me. Our views and knowledge have changed the way we look at certain traditions. However, we still long for simpler days when innocent fun was innocent fun and the image of a child beaming as his face entered the water will long stand as one of the symbols of Halloween.