In college I was part of a research lab that did alcohol behavior studies at student parties. One thing we learned early on: the presence of alcohol testing turns it into a drinking contest. At least with stupid young college boys.

We'd show up to a frat party with a survey and breathalyzers and got people to line up before things got ... weird. As soon as word caught on that we were measuring blood alcohol levels, the boys would start chugging alcohol at dangerous rates to see who could blow the highest BAC. So much for promoting safe drinking behavior! And this would obviously invalidate the research, so we had to go in like a strike team and collect as much data before word got out!