You can enjoy the festive atmosphere of the fair. You meet people who can help you with your business. You meet craftsmen who can give you support. The major disadvantage of selling through craft fairs is that it takes away from production. While you are selling, nothing is being produced.
Fairs can become boring when slow.
Information given at fairs can get repetitive. Traveling, setting up and taking down displays can cause fatigue. Display equipment can become costly. You must overcome the image of the fair as being a flea market where people give little respect to established prices. Since you come in direct contact with the buyer, you may have to cope with negative feedback.