We have always had at leat 3 dogs, our neighbor has 5 and they listen to him as Alpha, literally, the most well behaved dogs. Mine are excellent as well. However iti s true, unattended in a "pack" they will get in to trouble they would not normally get into. Fencing your yard is a great idea and I highly recommend it. Any dog with one or more are technically in a pack, and will act as such if left unattended. Expect it and prepare for it. Responsible ownership is a must with only one but even more with 2 or more. "Idle paws are the devils tools!" If you are fenced in and its safe and secure do not worry yourself to death, having a companion or two should not give you ulcers!