Per the housekeepers union and Disney, housekeeping gets paid more than other workers so no tip required. In addition they don't really do much for DVC rooms cleaning every 4 days.
We leave either $10 (1 bedroom) or $20 (2 bedroom) when we leave. (Seldom stay in a studio). We generally do not tip for Trash & Towel service. We do tip a few dollars if we ask housekeeping to bring us something that is missing from the room or something extra like a towel package.
Bill is right, Jessieroo. If you booked a Disney package on cash, you should have daily housekeeping. Enjoy! OKW is my home resort and my family LOVES OKW!
I would tip a dollar per person per day and additional if I requested anything above and beyond normal service. You are not required to tip but some of us do it.