Use of a replacement reservoir assembly for a dispensing system for replacing of a similar reservoir assembly, the dispensing system comprising: a reservoir assembly and an activation unit, the reservoir assembly removably coupled to the activation unit for replacement by a similar reservoir assembly, an electromagnetic radiation waveguide (64; 184; 200) having an inlet and outlet and providing a path for transmission of electromagnetic radiation from the inlet to the outlet, an electromagnetic radiation sensor (56, 72, 256, 356) carried by the activation unit sensing electromagnetic radiation from the waveguide via the outlet, an electromagnetic radiation emitter carried by the activation unit directing electromagnetic radiation into the waveguide via the inlet, and a control mechanism to permit operation of the dispensing system only when the electromagnetic radiation sensed by the sensor (56, 72, 256, 356) appropriately correlates to the electromagnetic radiation emitted by the emitter, the reservoir assembly including: a reservoir containing material to be dispensed and having an outlet opening for dispensing of the material therefrom, an outlet member secured to the outlet opening against removal from the reservoir, the outlet member when secured to the reservoir rendering the reservoir difficult to refill with material through the outlet opening, the reservoir aside from the outlet opening not having another opening by which material can be passed to refill the reservoir with the material, wherein at least part of the waveguide (64; 184; 200) is carried by the reservoir assembly and removable therewith, the waveguide comprising a frangible portion, wherein removal of the outlet member causing destruction of the frangible portion of the waveguide (64, 184, 200) which changes transmission characteristics of electromagnetic radiation from the inlet to the outlet via said path. a reservoir assembly and an activation unit, the reservoir assembly removably coupled to the activation unit for replacement by a similar reservoir assembly, an electromagnetic radiation waveguide (64; 184; 200) having an inlet and outlet and providing a path for transmission of electromagnetic radiation from the inlet to the outlet, an electromagnetic radiation sensor (56, 72, 256, 356) carried by the activation unit sensing electromagnetic radiation from the waveguide via the outlet, an electromagnetic radiation emitter carried by the activation unit directing electromagnetic radiation into the waveguide via the inlet, and a control mechanism to permit operation of the dispensing system only when the electromagnetic radiation sensed by the sensor (56, 72, 256, 356) appropriately correlates to the electromagnetic radiation emitted by the emitter, the reservoir assembly including: a reservoir containing material to be dispensed and having an outlet opening for dispensing of the material therefrom, an outlet member secured to the outlet opening against removal from the reservoir, the outlet member when secured to the reservoir rendering the reservoir difficult to refill with material through the outlet opening, the reservoir aside from the outlet opening not having another opening by which material can be passed to refill the reservoir with the material, wherein at least part of the waveguide (64; 184; 200) is carried by the reservoir assembly and removable therewith, the waveguide comprising a frangible portion, wherein removal of the outlet member causing destruction of the frangible portion of the waveguide (64, 184, 200) which changes transmission characteristics of electromagnetic radiation from the inlet to the outlet via said path. a reservoir containing material to be dispensed and having an outlet opening for dispensing of the material therefrom, an outlet member secured to the outlet opening against removal from the reservoir, the outlet member when secured to the reservoir rendering the reservoir difficult to refill with material through the outlet opening, the reservoir aside from the outlet opening not having another opening by which material can be passed to refill the reservoir with the material, wherein at least part of the waveguide (64; 184; 200) is carried by the reservoir assembly and removable therewith, the waveguide comprising a frangible portion, wherein removal of the outlet member causing destruction of the frangible portion of the waveguide (64, 184, 200) which changes transmission characteristics of electromagnetic radiation from the inlet to the outlet via said path.