I have a customer who has connected two buildings about 250 apart with an strand of cat5e cabliing strung on telephone poles. In the past he has experienced outages and switches on each end of this external strand getting burned up. I maintain since the buildings do not share the same common ground, there is the possibility that a potential exists in that cable and flow of unwanted current is a certainy. In my thirty years in the business I have never seen anything other than fiber or encrypted wireless beween buildings. A local cabling company saw no problem with using copper. I'm I in the majority or minority in my opinion that fiber is the way to go. There is a workstation in building A transmitting huge amounts of data to a server in building B to make matters more interestng.