• Malfunctions - These happen quite infrequently. But remember, you are dealing with an electronic device. With time, wear, or water, the possibility of malfunction will increase. If the collar is triggered and remains on, it will cause severe trauma and can be fatal to your dog (can cause severe burns).
• Locked Out - Your dog sees a bird or squirrel outside the property line, charges, and has gained so much momentum by the time it reaches the perimeter that it crosses the line and is afraid to come back. The animal is "locked out" of its own property. Some dogs will become anxious and run away.
• Other Dogs - Just because your dog won't cross the boundary to get out of the invisible fence doesn't mean that another dog won't cross the boundary to come in your yard, which may compromise your dogs safety, depending on the health and temperament of the other dog.
• Traumatization - Many dogs won't eat for days after receiving one or two shocks because they are so traumatized. For this reason, many trainers are averse to any type of shock training.
• Incorrect Training - Dogs who get shocked when trying to approach people passing by can associate the shock with the people, and thus become either overly aggressive or overly timid around people.

• Picking a Fence - All the Options: Article from Golden Retriever Rescue of Mid-Florida, Inc. (GRRMF) about selecting a fence type for your dog.
• Invisible Fencing: Problems with invisible fencing, from Great Pyrenees Rescue.
• Dogs Deserve Better:Dogs Deserve Better is a nonprofit organization dedicated to freeing the chained dog, and bringing our 'best friend' into the home and family.
• Friendly Fence:Friendly Fence is a virtually invisible, incredibly strong pet fence that safely keeps your dog and/or cat within a designated area without the use of electric wires or unattractive and costly fencing.

Also, we are all very negative on invisible fences, for many, many reasons. For one thing, even if your dog stays inside the "fence", it doesn't prevent any other people/animals from coming in. An aggressive dog could attack your dog, and your dog would have no place to hide.

Even a dog who is well trained to an invisible fence has a "trigger". With some, it is the sight of a deer or other animal. With others, it's thunder (if they're afraid of thunder). In these instances, very often a dog will go through the invisible fence due to excitement/fear. However, when the dog calms down, he/she will not cross the fence to come in. So essentially, your dog is trapped outside of the fence.

We have very rarely adopted dogs to folks with invisible fences, and then, only if they promised not to ever leave the dog unattended when he/she is out in the fenced area. They really give you a very false sense of security.

NOTE: My neighbors had a dog with ideopathic epilepsy. During one of her seizures, she went through the fence. A neighbor found her coming out of her seizure in the middle of the road. Fortunately, she was ok.

I've had first hand experience the last item, with the first CARE foster dog I adopted out. I used the bad judgement to let him go to a home with an invisible fence. They called a week and half later, saying that he was so traumatized that he had become unresponsive and obstinate, and they didn't think he would ever bond with them. Needless to say, I couldn't get there quickly enough to pick him up. The "unresponsive and obstinate" dog was completely overjoyed to see me and practically flung himself into arms and licked me all the way home. OK, can you blame me for adopting him myself after that?