I flew on UA942 ORD-CDG (3-class 767) two weeks ago and the lavatory situation was a total mess. I was in 17A E+ on the 100% full (and oversold) flight. Of course, the lavatories a few rows ahead of us were intended for C - however, as part of the new "security" measures, the curtains that were previously located behind them were gone. This created quite a few interesting conversations between passengers and crew...especially when the Y aisles were loaded with service carts. About an hour into the flight, the crew members took pieces of computer paper and scribbled out some "BATHROOM FOR BUSINESS PASSENGERS ONLY" One upset coach passenger even proceeded to rip one of those signs down later that evening...if only the crew had seen him I bet we would of been in Gander.