We've never experienced this, although I know other folks have.
If it happened to me, I'd handle it two ways. First of all, when I checked in and found what was wrong, I absolutely would not clean it up myself. I'd call housekeeping, let them know that I was not happy (without reaming them out, which just kills their motivation to help), and ask them to reclean the room ASAP. They'd very likely comply within a couple of hours. If not, I'd stay on top of them until they did.
Second, I'd certainly send an e-mail to the resort with a copy to Member Services. I'm quite confident that the email would get read, would be shared at the next staff meeting, and might even get me a return phone call. Each resort has customer service representatives and that's how they handle these things. If management saw that your email was part of a pattern, then they'd take action.
If we all followed a procedure like this, can you imagine how powerful an influence it would have on
DVC management?