The Hair Has to Go Somewhere
Cats are fastidious creatures and with all that grooming comes hair; it has to go somewhere! Normally the hair is passed along with food through the cat and comes out in the litter box, but sometimes it comes back out the other way. This is technically referred to as a trichobezoar, or a large mass of hair. Trichobezoars are formed in the stomach, but can sometimes be found in the esophagus. Unlike other species, cats do not have the same strong contractions (peristaltic movements) to move undigested contents, which may explain why they are more prone to throwing up hairballs.
Both cats with long and short hair are prone to forming hairballs. A hairball every now and then is not uncommon. Some reports show that 50-80% of cats vomit a hairball once a month. But continuous, repetitive vomiting of hair (or other material) may represent an underlying issue, and should be addressed by a veterinarian.
Hairballs are commonly treated with petroleum-based products to lube everything up, but stronger drugs may be recommended by your veterinarian. There are some new commercial diets that also claim to help in the reduction of hairball formation.