I always tip housekeepers. To me, they are undervalued and underpaid for the amount of work they perform. Don't blame them for lack of daily housekeeping, that's a management decision. I spent a few weeks in Australia recently, and while in Brisbane, I dutifully left a $5 AUD bill on the pillow each morning on my way out. Upon my return, the tip was always placed neatly on the night stand. This went on for three days until I encountered a housekeeper in the corridor and asked why my tip wasn't accepted. She told me I had to attach a note specifically stating it was a tip meant for the housekeeper lest she be accused of theft. I laughed and asked if she had serviced my room for the past three days. She sheepishly said she had, but only once. She was most reticent to accept the tip I handed her.