1. All sorts of STDs
Everyone knows that the REAL goal of the Olympics is to give athletes and their coteries a safe space for orgies -- the Olympics is a fuckfest, basically, and if they just called it Rio Fuckfest 2016, Brazil could save itself from wasting money on stadiums, pools, and light rail.
Looking for the requisite outrageous number of free condoms being distributed to the Olympic Village this year? It's 450,000, enough for each athlete to have sex 84 times, which is just shy of four times per day over three weeks, not accounting for breakage or misuse or blowing them up and making silly balloon animals. They're going to need more condoms, is the point.
And that's just the athletes! Think of all the visitors, tourists, and locals looking for Rio 2016 to serve as their wingman. The only problem with shipping strangers from around the world into one city to bang, is: STDs. Even the CDC warns that the "celebratory atmosphere" could lead to risky sex. On the other hand, "to have more sex" might be the only defensible reason to host the Olympics at this point.