Okay, My turn. I would love to make the argument of safety as a reason for requiring bathrooms be on their own circuit. Using the hair dryer and teenage girl scenario, everyone seems to wait to the last minute to get ready to go somewhere, including wifey. Now, compound that with teenaged friends. If you can't dry your hair in another bathroom without tripping the breaker, extension cords are drug in through the doorway so they can use the mirror. Now, you have created a situation where an unprotected extension cord must be used. This is not an uncommon occurrence that is directly attributable to the fact that multiple bathrooms are all on one circuit. I agree, can't wire a house for all possible scenarios, however, this issue can easily be resolved. I personally put all bathrooms on separate circuits.