> The Silicone sponge is perfectly hygienic. Its completely airy ("open-cell") structure does not keep dirt or bacteria, is easily washable and dries fast. Silicone is perfectly anti-microbial, no dirt adheres to it.
This sounds like a dubious claim. I've seen dirty sponges with fungus and all sorts growing on them, why should this be any different?
Also what about mineral buildup from hard water? Surely the microbes can adhere to that too.