Boarding your dog with a friend can definitly be a good thing for him/her, however in certain situations it might not be best. If you have two dogs (and get along), it is of course always best to have them in the same enclosure. Dogs are pack animals, and are very social and thus prefer being with other pack members to keep them company especially in new environments. Boarding your dog with an unfamiliar dog is not a good idea, the dogs should always meet each other and spend enough time with each other to feel comfortable with each other. It definitly would not be a good thing if they got into a fight during the night.