Hate to say this everyone, but this has been going on a long time. When I was a teenager, that is what we did. And like fatfreek said, do not blame the workers, this is management's fault by not putting in place a dishwasher on the floors and/or full carts of clean glasses from the kitchen that can be used. When you are a chambermaid...you are under time constraints. You have a quota to get as many rooms done in a certain time period. But still, yes it is gross, I will bring my own disposible cup for now on.
Joanne