There were people behind me who had (larger) refillable cups of something, that weren't the refillable sippy cups sold by Wolftrap. And though it looked like their cups had secure tops, they still managed to spill some of their beverage all over my head and back as they stumbled to their seats.
Perhaps if they had invested in the $6 sippy cups,. this would not have happened. People at concerts tend not to really care about the people who are around them, so I figured it's par for the course. I was just glad people decided to stay seated for all three acts.