It looks like rain water, and other natural elements are just as hazardous as the water from your own though the danger of the toilet is probably increased due to the fact that people feel more at ease at home and are likely to be more careless with their possessions. Other locations where phones suffer water damage: in a drink (or a drink spilled onto it), in the bath or shower, in the kitchen sink and of course forgetting to take it out of a pocket before sending the pants into a washing machine.
I guess you can never go wrong with having some phone insurance these days. How many of you have damaged your phones with water before? Any interesting stories to share?