Sanitation

Do remember that scene in The Matrix where the one trench coat guy says to the other "do you think that's air you're breathing?" It's hard to remember the point of a movie that came out 15 years ago, but I think it had something to do with sanitation.

Sanitation is the process through which an organization of lifeforms creates conditions that are adverse to lifeforms of another species, provided that the latter species may have an negative effect on the livelihood and wellbeing of the former. For example, a butcher in a hotdog factory has to clear out the meat chutes every once in a while, lest the rotting meat attracted a pack of wild dogs that would overrun the facility and make it harder for him to do his job. Similarly, ancient Romans devised a series of interconnected ducts to carry away human waste, (mainly excrement and urine), from their urban centres to prevent the spread of disease.

All around, their are really no drawbacks to sanitation. It's basically a "killer app," where that which is being killed is feral dogs and cholera.