Using refillable dispensers is already common practice in many parts of the world and everybody seems quite happy with it. It has started to show up in the US as well, and I've even seen just last night in my New York hotel.
In most cases the dispensers are mounted upside down on the wall and you dispense by squeezing the dispenser, pushing something up, or turning a knob/handle. It's not unlike the soap dispensers you see in many public rest rooms.
Overall it works well and is super convenient. It would be difficult to tamper with, but then again, everything can potentially be tampered with. However, the likelihood is extremely small and there is really no motivation to do it