I flew with an airline that banned bottles in the overhead lockers, if anyone remembers Air 2000. They were pretty thorough when it came to SEP. I think it was something to do with findings from a crash investigation - possibly the Korean Airlines crash in Guam but don't quote me. Anyway, I remember it being a pain, especially with people sitting at the overwing exits where you couldn't stow anything on the floor or bottles in the overheads.