I agree dogs that are not socialised are likely to have little exposure to most everyday life occurrences,noises etc and will lack insight and interpretation towards many senarios.Lack of socialisation can cause weak nerve even if the dog has the best genetic attributes for a good gaurding animal.The enviromental influences on the character and temperment of the dog cannot be under estimated .A good gaurd dog is a confident self assured animal that  can be taken anywhere and tolerate anything.Its gaurding abilities kicking in when it is needed and only when needed.