No way! Foam parties are so much fun! I used to go to them at frat houses in college (which is where my sister went last night). I will ask her later how it was, she's still sleeping now.
It is not stupid. It's fun! You wear shorts and tank tops/t-shirts, go barefoot, dance around with music playing and foam everywhere, everyone is slippery and wet and having a great time. And most people are drunk/high usually, it's just a lot of fun.
My mother in law is in town and we are getting away for one night. However, we are entertaining clients. It should be nice and also fun. Tonight - friends in the suburbs.