Heard from a reputable person, a Tuscaloosa principle, that it appears to be mostly high schoolers making a game out of it. He knows for a fact that a group of his students participated in at least one of these parties. Everyone shows up to the party and puts money in the pot and the first person that can come up with a verifiable positive test in the days following the party, gets all the money in the pot. It's winner take all and 2nd place finisher is just the first loser.