My guess is that the ice machine never gets cleaned....and the grubby little hands that work at these places are all over the ice.....
Yeah, agreed. Anyone that's worked in a restaurant knows how many hands go into ice makers when "no one's looking."
Also, what kind of bacteria is in each? There may be more in the ice, but if what's in the toilet water can cause disintery or the like, then wouldn't that mean that the TW is worse? IDK, I'm not a microbiologist.